@article{marshall_setoodehnia_portillo_kelley_longland_2021, title={New energy for the 133-keV resonance in the Na-23(p, gamma) Mg-24 reaction and its impact on nucleosynthesis in globular clusters}, volume={104}, ISSN={["2469-9993"]}, url={https://doi.org/10.1103/PhysRevC.104.L032801}, DOI={10.1103/PhysRevC.104.L032801}, abstractNote={Globular cluster stars exhibit star-to-star anticorrelations between oxygen and sodium in their atmospheres. An improved description of the sodium-destroying $^{23}\mathrm{Na}+\mathrm{p}$ reaction rates is essential to understanding these observations. We present an energy analysis of $^{24}\mathrm{Mg}$ states based on a new measurement of the $^{23}\mathrm{Na}(^{3}\mathrm{He},\mathrm{d})^{24}\mathrm{Mg}$ reaction. A key resonance in $^{23}\mathrm{Na}(\mathrm{p},\ensuremath{\gamma})^{24}\mathrm{Mg}$ is found to be at ${E}_{r}^{\text{c.m.}}=133(3)$ keV, 5 keV lower than previously adopted. This finding has a dramatic effect on the $^{23}\mathrm{Na}(\mathrm{p},\ensuremath{\gamma})^{24}\mathrm{Mg}$ reaction rate, increasing it by a factor of 2 for the recommended rate. The nucleosynthesis impact of this change is investigated.}, number={3}, journal={PHYSICAL REVIEW C}, author={Marshall, C. and Setoodehnia, K. and Portillo, F. and Kelley, J. H. and Longland, R.}, year={2021}, month={Sep} } @article{dimitriou_basunia_bernstein_chen_elekes_huang_hurst_iimura_jain_kelley_et al._2020, title={International network of nuclear structure and decay data evaluators}, volume={239}, ISSN={["2100-014X"]}, DOI={10.1051/epjconf/202023915004}, abstractNote={Compilation, evaluation and dissemination of nuclear data are arduous tasks that rely on contributions from experts in both the basic and applied sciences communities whose efforts are coordinated by the International Atomic Energy Agency (IAEA). The Evaluated Nuclear Structure Data File (ENSDF) includes the most extensive and comprehensive set of nuclear structure and decay data evaluations performed by the international network of Nuclear Structure and Decay Data evaluators (NSDD) under the auspices of the IAEA. In this report we describe the recent NSDD activities supported by the IAEA and provide some future perspectives.}, journal={ND 2019: INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY}, author={Dimitriou, Paraskevi and Basunia, Shamsuzzoha and Bernstein, Lee and Chen, Jun and Elekes, Zoltan and Huang, Xiaolong and Hurst, Aaron and Iimura, Hideki and Jain, Ashok Kumar and Kelley, John and et al.}, year={2020} } @article{tonchev_tsoneva_goriely_bhatia_arnold_hammond_kelley_kwan_lenske_piekarewicz_et al._2018, title={Astrophysical relevance of the low-energy dipole strength of Pb-206}, volume={178}, ISSN={["2100-014X"]}, DOI={10.1051/epjconf/201817804003}, abstractNote={The dipole strength of 206Pb was studied below the neutron separation energy using photon scattering experiments at the HIGS facility. Utilizing the technique of nuclear resonance fluorescence with 100% linearly-polarized photon beams, the spins, parities, branching ratios and decay widths of excited states in 206Pb from 4.9 - 8.1 MeV have been measured. The new experimental information is used to reliably predict the neutron capture cross section of 205Pb, an important branch point nucleus along the s-process path of nucleosynthesis.}, journal={16TH INTERNATIONAL SYMPOSIUM ON CAPTURE GAMMA-RAY SPECTROSCOPY AND RELATED TOPICS (CGS16)}, author={Tonchev, A. P. and Tsoneva, N. and Goriely, S. and Bhatia, C. and Arnold, C. W. and Hammond, S. L. and Kelley, J. H. and Kwan, E. and Lenske, H. and Piekarewicz, J. and et al.}, year={2018} } @inproceedings{tonchev_stoyer_becker_macri_ryan_sheets_gooden_arnold_bond_bredeweg_et al._2018, title={Energy evolution of the fission-product yields from neutron-induced fission of U-235, U-238, and PU-239: an unexpected observation}, booktitle={Fission and Properties of Neutron-Rich Nuclei}, author={Tonchev, A. P. and Stoyer, M. A. and Becker, J. A. and Macri, R. and Ryan, C. and Sheets, S. A. and Gooden, M. E. and Arnold, C. W. and Bond, E. and Bredeweg, T. and et al.}, year={2018}, pages={381–388} } @article{setoodehnia_marshall_kelley_liang_chaves_longland_2018, title={Excited states of Ca-39 and their significance in nova nucleosynthesis}, volume={98}, ISSN={["2469-9993"]}, DOI={10.1103/PhysRevC.98.055804}, abstractNote={Background: Discrepancies exist between the observed abundances of argon and calcium in oxygen-neon nova ejecta and those predicted by nova models. An improved characterization of the $^{38}$K($p, \gamma$)$^{39}$Ca reaction rate over the nova temperature regime ($\sim$ 0.1 -- 0.4 GK), and thus the nuclear structure of $^{39}$Ca above the proton threshold (5770.92(63) keV), is necessary to resolve these contradictions. Purpose: The present study was performed to search for low-spin proton resonances in the $^{38}$K $+$ $p$ system, and to improve the uncertainties in energies of the known astrophysically significant proton resonances in $^{39}$Ca. Method: The level structure of $^{39}$Ca was investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the $^{40}$Ca($^{3}$He, $\alpha$)$^{39}$Ca reaction. Differential cross sections were measured over 6 laboratory angles at 21 MeV. Distorted-wave Born approximation calculations were performed to constrain the spin-parity assignments of observed levels with special attention to those significant in determination of the $^{38}$K($p, \gamma$)$^{39}$Ca reaction rate over the nova temperature regime. Results: The resonance energies corresponding to two out of three astrophysically important states at 6154(5) and 6472.2(24) keV are measured with better precision than previous charged-particle spectroscopy measurements. A tentatively new state is discovered at 5908(3) keV. The spin-parity assignments of a few of the astrophysically important resonances are determined. Conclusions: The present $^{38}$K($p, \gamma$)$^{39}$Ca upper limit thermonuclear reaction rate at 0.1 -- 0.4 GK is higher than that determined in [Physical Review C 97 (2018) 025802] by at most a factor of 1.4 at 0.1 GK.}, number={5}, journal={PHYSICAL REVIEW C}, publisher={American Physical Society (APS)}, author={Setoodehnia, K. and Marshall, C. and Kelley, J. H. and Liang, J. and Chaves, F. Portillo and Longland, R.}, year={2018}, month={Nov} } @article{tonchev_escher_scielzo_bedrossian_ilieva_humby_cooper_goddard_werner_tornow_et al._2017, title={Capture cross sections on unstable nuclei}, volume={146}, ISSN={2100-014X}, url={http://dx.doi.org/10.1051/EPJCONF/201714601013}, DOI={10.1051/EPJCONF/201714601013}, abstractNote={Accurate neutron-capture cross sections on unstable nuclei near the line of beta stability are crucial for understanding the s -process nucleosynthesis. However, neutron-capture cross sections for short-lived radionuclides are difficult to measure due to the fact that the measurements require both highly radioactive samples and intense neutron sources. Essential ingredients for describing the γ decays following neutron capture are the γ-ray strength function and level densities. We will compare different indirect approaches for obtaining the most relevant observables that can constrain Hauser-Feshbach statistical-model calculations of capture cross sections. Specifically, we will consider photon scattering using monoenergetic and 100% linearly polarized photon beams. Challenges that exist on the path to obtaining neutron-capture cross sections for reactions on isotopes near and far from stability will be discussed.}, journal={EPJ Web of Conferences}, publisher={EDP Sciences}, author={Tonchev, A.P. and Escher, J.E. and Scielzo, N. and Bedrossian, P. and Ilieva, R.S. and Humby, P. and Cooper, N. and Goddard, P.M. and Werner, V. and Tornow, W. and et al.}, editor={Plompen, A. and Hambsch, F.-J. and Schillebeeckx, P. and Mondelaers, W. and Heyse, J. and Kopecky, S. and Siegler, P. and Oberstedt, S.Editors}, year={2017}, pages={01013} } @inproceedings{tonchev_escher_scielzo_bedrossian_ilieva_humby_cooper_goddard_werner_tornow_et al._2017, title={Capture cross sections on unstable nuclei}, volume={146}, booktitle={Nd 2016: international conference on nuclear data for science and technology}, author={Tonchev, A. P. and Escher, J. E. and Scielzo, N. and Bedrossian, P. and Ilieva, R. S. and Humby, P. and Cooper, N. and Goddard, P. M. and Werner, V. and Tornow, W. and et al.}, year={2017} } @article{kelley_purcell_sheu_2017, title={Energy levels of light nuclei A=12}, volume={968}, ISSN={["1873-1554"]}, DOI={10.1016/j.nuclphysa.2017.07.015}, abstractNote={A review of evidence on the properties of the A=12 nuclei, with emphasis on material leading to information about the structure of the A=12 systems.}, journal={NUCLEAR PHYSICS A}, author={Kelley, J. H. and Purcell, J. E. and Sheu, C. G.}, year={2017}, month={Dec}, pages={71–253} } @article{tonchev_tsoneva_bhatia_arnold_goriely_hammond_kelley_kwan_lenske_piekarewicz_et al._2017, title={Pygmy and core polarization dipole modes in 206 Pb: Connecting nuclear structure to stellar nucleosynthesis}, volume={773}, ISSN={0370-2693}, url={http://dx.doi.org/10.1016/J.PHYSLETB.2017.07.062}, DOI={10.1016/J.PHYSLETB.2017.07.062}, abstractNote={A high-resolution study of the electromagnetic response of 206Pb below the neutron separation energy is performed using a (γ→,γ′) experiment at the HIγ→S facility. Nuclear resonance fluorescence with 100% linearly polarized photon beams is used to measure spins, parities, branching ratios, and decay widths of excited states in 206Pb from 4.9 to 8.1 MeV. The extracted ΣB(E1)↑ and ΣB(M1)↑ values for the total electric and magnetic dipole strength below the neutron separation energy are 0.9±0.2e2fm2 and 8.3±2.0μN2, respectively. These measurements are found to be in very good agreement with the predictions from an energy-density functional (EDF) plus quasiparticle phonon model (QPM). Such a detailed theoretical analysis allows to separate the pygmy dipole resonance from both the tail of the giant dipole resonance and multi-phonon excitations. Combined with earlier photonuclear experiments above the neutron separation energy, one extracts a value for the electric dipole polarizability of 206Pb of αD=122±10mb/MeV. When compared to predictions from both the EDF+QPM and accurately calibrated relativistic EDFs, one deduces a range for the neutron-skin thickness of Rskin206=0.12–0.19fm and a corresponding range for the slope of the symmetry energy of L=48–60MeV. This newly obtained information is also used to estimate the Maxwellian-averaged radiative cross section Pb205(n,γ)Pb206 at 30 keV to be σ=130±25mb. The astrophysical impact of this measurement—on both the s-process in stellar nucleosynthesis and on the equation of state of neutron-rich matter—is discussed.}, journal={Physics Letters B}, publisher={Elsevier BV}, author={Tonchev, A.P. and Tsoneva, N. and Bhatia, C. and Arnold, C.W. and Goriely, S. and Hammond, S.L. and Kelley, J.H. and Kwan, E. and Lenske, H. and Piekarewicz, J. and et al.}, year={2017}, month={Oct}, pages={20–25} } @article{benouaret_beller_pai_pietralla_ponomarev_romig_schnorrenberger_zweidinger_scheck_isaak_et al._2016, title={Dipole response of the odd-proton nucleus 205Tl up to the neutron-separation energy}, volume={43}, ISSN={0954-3899 1361-6471}, url={http://dx.doi.org/10.1088/0954-3899/43/11/115101}, DOI={10.1088/0954-3899/43/11/115101}, abstractNote={The low-lying electromagnetic dipole strength of the odd-proton nuclide 205Tl has been investigated up to the neutron separation energy exploiting the method of nuclear resonance fluorescence. In total, 61 levels of 205Tl have been identified. The measured strength distribution of 205Tl is discussed and compared to those of even–even and even–odd mass nuclei in the same mass region as well as to calculations that have been performed within the quasi-particle phonon model.}, number={11}, journal={Journal of Physics G: Nuclear and Particle Physics}, publisher={IOP Publishing}, author={Benouaret, N and Beller, J and Pai, H and Pietralla, N and Ponomarev, V Yu and Romig, C and Schnorrenberger, L and Zweidinger, M and Scheck, M and Isaak, J and et al.}, year={2016}, month={Oct}, pages={115101} } @article{gooden_arnold_becker_bhatia_bhike_bond_bredeweg_fallin_fowler_howell_et al._2016, title={Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV}, volume={131}, ISSN={0090-3752}, url={http://dx.doi.org/10.1016/J.NDS.2015.12.006}, DOI={10.1016/J.NDS.2015.12.006}, abstractNote={Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varying degrees of systematic errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for 235U, 238U and 239Pu. The measurements have been performed at TUNL, using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual-fission chamber and gamma-ray counted using shielded HPGe detectors for a period of 1-2 months to determine the yield of various fission products. To the extent possible all irradiation and counting procedures were kept the same to minimize sources of systematic errors. FPY have been determined at incident neutron energies of 0.6, 1.4, 2.4, 3.5, 4.6, 5.5, 8.9 and 14.8 MeV.}, journal={Nuclear Data Sheets}, publisher={Elsevier BV}, author={Gooden, M.E. and Arnold, C.W. and Becker, J.A. and Bhatia, C. and Bhike, M. and Bond, E.M. and Bredeweg, T.A. and Fallin, B. and Fowler, M.M. and Howell, C.R. and et al.}, year={2016}, month={Jan}, pages={319–356} } @article{löher_savran_aumann_beller_bhike_cooper_derya_duchêne_endres_hennig_et al._2016, title={The decay pattern of the Pygmy Dipole Resonance of 140Ce}, volume={756}, ISSN={0370-2693}, url={http://dx.doi.org/10.1016/J.PHYSLETB.2016.02.042}, DOI={10.1016/J.PHYSLETB.2016.02.042}, abstractNote={The decay properties of the Pygmy Dipole Resonance (PDR) have been investigated in the semi-magic N=82 nucleus 140Ce using a novel combination of nuclear resonance fluorescence and γ–γ coincidence techniques. Branching ratios for transitions to low-lying excited states are determined in a direct and model-independent way both for individual excited states and for excitation energy intervals. Comparison of the experimental results to microscopic calculations in the quasi-particle phonon model exhibits an excellent agreement, supporting the observation that the Pygmy Dipole Resonance couples to the ground state as well as to low-lying excited states. A 10% mixing of the PDR and the [21+×PDR] is extracted.}, journal={Physics Letters B}, publisher={Elsevier BV}, author={Löher, B. and Savran, D. and Aumann, T. and Beller, J. and Bhike, M. and Cooper, N. and Derya, V. and Duchêne, M. and Endres, J. and Hennig, A. and et al.}, year={2016}, month={May}, pages={72–76} } @article{loher_savran_aumann_beller_bhike_cooper_derya_duchene_endres_hennig_et al._2016, title={The decay pattern of the Pygmy Dipole Resonance of Ce-140}, volume={756}, journal={Physics Letters. B}, author={Loher, B. and Savran, D. and Aumann, T. and Beller, J. and Bhike, M. and Cooper, N. and Derya, V. and Duchene, M. and Endres, J. and Hennig, A. and et al.}, year={2016}, pages={72–76} } @inproceedings{isaak_loher_savran_aumann_beller_cooper_derya_duchene_endres_fiori_et al._2015, title={Decay pattern of the Pygmy Dipole Resonance in Ce-140}, volume={93}, booktitle={Cgs15 - capture gamma-ray spectroscopy and related topics}, author={Isaak, J. and Loher, B. and Savran, D. and Aumann, T. and Beller, J. and Cooper, N. and Derya, V. and Duchene, M. and Endres, J. and Fiori, E. and et al.}, year={2015} } @inproceedings{isaak_löher_savran_aumann_beller_cooper_derya_duchêne_endres_fiori_et al._2015, title={Decay pattern of the Pygmy Dipole Resonance in140Ce}, volume={93}, ISSN={2100-014X}, url={http://dx.doi.org/10.1051/EPJCONF/20159301048}, DOI={10.1051/EPJCONF/20159301048}, abstractNote={The decay behavior of low-lying dipole states in 140Ce was investigated exploiting the γ3-setup at the HIγS facility using quasi-monochromatic photon beams. Branching ratios of individual excited states as well as average branching ratios to low-lying states have been extracted using γ – γ coincidence measurements. The comparison of the average branching ratios to QPM calculations shows a remarkable agreement between experiment and theory in the energy range from 5.0 to 8.5 MeV.}, booktitle={EPJ Web of Conferences}, publisher={EDP Sciences}, author={Isaak, J. and Löher, B. and Savran, D. and Aumann, T. and Beller, J. and Cooper, N. and Derya, V. and Duchêne, M. and Endres, J. and Fiori, E. and et al.}, editor={Schwengner, R. and Zuber, K.Editors}, year={2015}, pages={01048} } @article{werner_cooper_goddard_humby_ilieva_rusev_beller_bernards_crider_isaak_et al._2015, title={Dipole strength distributions from HIGS Experiments}, volume={93}, ISSN={2100-014X}, url={http://dx.doi.org/10.1051/EPJCONF/20159301031}, DOI={10.1051/EPJCONF/20159301031}, abstractNote={A series of photon scattering experiments has been performed on the double-beta decay partners 76 Ge and 76 Se, in order to investigate their dipole response up to the neutron separation threshold. Gamma-ray beams from bremsstrahlung at the S-DALINAC and from Compton-backscattering at HIGS have been used to measure absolute cross sections and parities of dipole excited states, respectively. The HIGS data allows for indirect measurement of averaged branching ratios, which leads to significant corrections in the observed excitation cross sections. Results are compared to statistical calculations, to test photon strength functions and the Axel-Brink hypothesis.}, journal={EPJ Web of Conferences}, publisher={EDP Sciences}, author={Werner, V. and Cooper, N. and Goddard, P.M. and Humby, P. and Ilieva, R.S. and Rusev, G. and Beller, J. and Bernards, C. and Crider, B.P. and Isaak, J. and et al.}, editor={Schwengner, R. and Zuber, K.Editors}, year={2015}, pages={01031} } @article{bhatia_fallin_gooden_howell_kelley_tornow_arnold_bond_bredeweg_fowler_et al._2015, title={Exploratory study of fission product yields of neutron-induced fission of U-235, U-238, and Pu-239 at 8.9 MeV}, volume={91}, number={6}, journal={Physical Review. C, Nuclear Physics}, author={Bhatia, C. and Fallin, B. F. and Gooden, M. E. and Howell, C. R. and Kelley, J. H. and Tornow, W. and Arnold, C. W. and Bond, E. and Bredeweg, T. A. and Fowler, M. M. and et al.}, year={2015} } @article{tonchev_bhatia_kelley_raut_rusev_tornow_tsoneva_2015, title={Nuclear Structure Studies with Gamma-Ray Beams}, volume={93}, ISSN={2100-014X}, url={http://dx.doi.org/10.1051/EPJCONF/20159301030}, DOI={10.1051/EPJCONF/20159301030}, abstractNote={In stable and weakly bound neutron-rich nuclei, a resonance-like concentration of dipole states has been observed for excitation energies below the neutron-separation energy. This clustering of strong dipole states has been named the Pygmy Dipole Resonance (PDR) in contrast to the Giant Dipole Resonance (GDR) that dominates the E1 response. Understanding the PDR is presently of great interest in nuclear structure and nuclear astrophysics. High-sensitivity studies of E1 and M1 transitions in closed-shell nuclei using monoenergetic and 100% linearly-polarized photon beams are presented.}, journal={EPJ Web of Conferences}, publisher={EDP Sciences}, author={Tonchev, Anton and Bhatia, Chitra and Kelley, John and Raut, Rajarshi and Rusev, Gencho and Tornow, Werner and Tsoneva, Nadia}, editor={Schwengner, R. and Zuber, K.Editors}, year={2015}, pages={01030} } @inproceedings{tonchev_bhatia_kelley_raut_rusev_tornow_tsoneva_2015, title={Nuclear structure studies with gamma-ray beams}, volume={93}, booktitle={Cgs15 - capture gamma-ray spectroscopy and related topics}, author={Tonchev, A. and Bhatia, C. and Kelley, J. and Raut, R. and Rusev, G. and Tornow, W. and Tsoneva, N.}, year={2015} } @inproceedings{benouaret_beller_isaak_kelley_pai_pietralla_ponomarev_raut_romig_rusev_et al._2015, title={QPM Analysis of 205Tl Nuclear Excitations below the Giant Dipole Resonance}, volume={93}, ISSN={2100-014X}, url={http://dx.doi.org/10.1051/EPJCONF/20159301044}, DOI={10.1051/EPJCONF/20159301044}, abstractNote={We analysed our experimental recent findings of the dipole response of the odd-mass stable nucleus 205 Tl within the quasi-particle phonon model. Using the phonon basis constructed for the neighbouring 204 Hg and wave function configurations for 205 Tl consisting of a mixture of quasiparticle ⊗ N-phonon configurations (N=0,1,2), only one group of fragmented dipole excited states has been reproduced at 5.5 MeV in comparison to the experimental distribution which shows a second group at about 5 MeV. The computed dipole transition strengths are mainly of E1 character which could be associated to the pygmy dipole resonance.}, booktitle={EPJ Web of Conferences}, publisher={EDP Sciences}, author={Benouaret, N. and Beller, J. and Isaak, J. and Kelley, J.H. and Pai, H. and Pietralla, N. and Ponomarev, V.Yu. and Raut, R. and Romig, C. and Rusev, G. and et al.}, editor={Schwengner, R. and Zuber, K.Editors}, year={2015}, pages={01044} } @inproceedings{benouaret_beller_isaak_kelley_pai_pietralla_ponomarev_raut_romig_rusev_et al._2015, title={QPM analysis of Tl-205 nuclear excitations below the giant dipole resonance}, volume={93}, booktitle={Cgs15 - capture gamma-ray spectroscopy and related topics}, author={Benouaret, N. and Beller, J. and Isaak, J. and Kelley, J. H. and Pai, H. and Pietralla, N. and Ponomarev, V. Y. and Raut, R. and Romig, C. and Rusev, G. and et al.}, year={2015} } @article{beller_stumpf_scheck_pietralla_deleanu_filipescu_glodariu_haxton_idini_kelley_et al._2015, title={Separation of the 1(+)/1(-) parity doublet in Ne-20}, volume={741}, journal={Physics Letters. B}, author={Beller, J. and Stumpf, C. and Scheck, M. and Pietralla, N. and Deleanu, D. and Filipescu, D. M. and Glodariu, T. and Haxton, W. and Idini, A. and Kelley, J. H. and et al.}, year={2015}, pages={128–133} } @article{beller_stumpf_scheck_pietralla_deleanu_filipescu_glodariu_haxton_idini_kelley_et al._2015, title={Separation of the 1+/1−parity doublet in 20 Ne}, volume={741}, ISSN={0370-2693}, url={http://dx.doi.org/10.1016/J.PHYSLETB.2014.12.018}, DOI={10.1016/J.PHYSLETB.2014.12.018}, abstractNote={The (J,T)=(1,1) parity doublet in 20Ne at 11.26 MeV is a good candidate to study parity violation in nuclei. However, its energy splitting is known with insufficient accuracy for quantitative estimates of parity violating effects. To improve on this unsatisfactory situation, nuclear resonance fluorescence experiments using linearly and circularly polarized γ-ray beams were used to determine the energy difference of the parity doublet ΔE=E(1−)−E(1+)=−3.2(±0.7)stat(−1.2+0.6)sys keV and the ratio of their integrated cross sections Is,0(+)/Is,0(−)=29(±3)stat(−7+14)sys. Shell-model calculations predict a parity-violating matrix element having a value in the range 0.46–0.83 eV for the parity doublet. The small energy difference of the parity doublet makes 20Ne an excellent candidate to study parity violation in nuclear excitations.}, journal={Physics Letters B}, publisher={Elsevier BV}, author={Beller, J. and Stumpf, C. and Scheck, M. and Pietralla, N. and Deleanu, D. and Filipescu, D.M. and Glodariu, T. and Haxton, W. and Idini, A. and Kelley, J.H. and et al.}, year={2015}, month={Feb}, pages={128–133} } @article{bhatia_fallin_gooden_howell_kelley_tornow_arnold_bond_bredeweg_fowler_et al._2014, title={Dual-fission chamber and neutron beam characterization for fission product yield measurements using monoenergetic neutrons}, volume={757}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2014.03.022}, DOI={10.1016/J.NIMA.2014.03.022}, abstractNote={A program has been initiated to measure the energy dependence of selected high-yield fission products used in the analysis of nuclear test data. We present out initial work of neutron activation using a dual-fission chamber with quasi-monoenergetic neutrons and gamma-counting method. Quasi-monoenergetic neutrons of energies from 0.5 to 15 MeV using the TUNL 10 MV FM tandem to provide high-precision and self-consistent measurements of fission product yields (FPY). The final FPY results will be coupled with theoretical analysis to provide a more fundamental understanding of the fission process. To accomplish this goal, we have developed and tested a set of dual-fission ionization chambers to provide an accurate determination of the number of fissions occurring in a thick target located in the middle plane of the chamber assembly. Details of the fission chamber and its performance are presented along with neutron beam production and characterization. Also presented are studies on the background issues associated with room-return and off-energy neutron production. We show that the off-energy neutron contribution can be significant, but correctable, while room-return neutron background levels contribute less than <1% to the fission signal.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Bhatia, C. and Fallin, B. and Gooden, M.E. and Howell, C.R. and Kelley, J.H. and Tornow, W. and Arnold, C.W. and Bond, E.M. and Bredeweg, T.A. and Fowler, M.M. and et al.}, year={2014}, month={Sep}, pages={7–19} } @article{bhatia_fallin_howell_tornow_gooden_kelley_arnold_bond_bredeweg_fowler_et al._2014, title={Fission Product Yield Study of 235U, 238U and 239Pu Using Dual-Fission Ionization Chambers}, volume={119}, ISSN={0090-3752}, url={http://dx.doi.org/10.1016/J.NDS.2014.08.089}, DOI={10.1016/J.NDS.2014.08.089}, abstractNote={Abstract To resolve long-standing differences between LANL and LLNL regarding the correct fission basis for analysis of nuclear test data [M.B. Chadwick et al., Nucl. Data Sheets 111, 2891 (2010); H. Selby et al., Nucl. Data Sheets 111, 2891 (2010)], a collaboration between TUNL/LANL/LLNL has been established to perform high-precision measurements of neutron induced fission product yields. The main goal is to make a definitive statement about the energy dependence of the fission yields to an accuracy better than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed the design, fabrication and testing of three dual-fission chambers dedicated to 235U, 238U, and 239Pu. The dual-fission chambers were used to make measurements of the fission product activity relative to the total fission rate, as well as for high-precision absolute fission yield measurements. The activation method was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and 14.5 MeV were produced via the 2H(d,n)3He reaction, and for neutrons at 14.8 MeV, the 3H(d,n)4He reaction was used. After activation, the induced γ-ray activity of the fission products was measured for two months using high-resolution HPGe detectors in a low-background environment. Results for the yield of seven fission fragments of 235U, 238U, and 239Pu and a comparison to available data at other energies are reported. For the first time results are available for neutron energies between 2 and 14 MeV.}, journal={Nuclear Data Sheets}, publisher={Elsevier BV}, author={Bhatia, C. and Fallin, B. and Howell, C. and Tornow, W. and Gooden, M. and Kelley, J. and Arnold, C. and Bond, E. and Bredeweg, T. and Fowler, M. and et al.}, year={2014}, month={May}, pages={324–327} } @article{derya_savran_endres_harakeh_hergert_kelley_papakonstantinou_pietralla_ponomarev_roth_et al._2014, title={Isospin properties of electric dipole excitations in Ca-48}, volume={730}, DOI={10.1016/j.physletb.2014.01.050}, abstractNote={Two different experimental approaches were combined to study the electric dipole strength in the doubly-magic nucleus 48Ca below the neutron threshold. Real-photon scattering experiments using bremsstrahlung up to 9.9 MeV and nearly mono-energetic linearly polarized photons with energies between 6.6 and 9.51 MeV provided strength distribution and parities, and an (α,α′γ) experiment at Eα=136MeV gave cross sections for an isoscalar probe. The unexpected difference observed in the dipole response is compared to calculations using the first-order random-phase approximation and points to an energy-dependent isospin character. A strong isoscalar state at 7.6 MeV was identified for the first time supporting a recent theoretical prediction.}, journal={Physics Letters. B}, author={Derya, V. and Savran, D. and Endres, J. and Harakeh, M. N. and Hergert, H. and Kelley, J. H. and Papakonstantinou, P. and Pietralla, N. and Ponomarev, V. Y. and Roth, R. and et al.}, year={2014}, pages={288–292} } @article{massarczyk_rusev_schwengner_doenau_bhatia_gooden_kelley_tonchev_tornow_2014, title={Magnetic dipole strength in Xe-128 and Xe-134 in the spin-flip resonance region}, volume={90}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.90.054310}, abstractNote={The magnetic dipole strength in the energy region of the spin-flip resonance is investigated in $^{128}\mathrm{Xe}$ and $^{134}\mathrm{Xe}$ using quasimonoenergetic and linearly polarized $\ensuremath{\gamma}$-ray beams at the High-Intensity $\ensuremath{\gamma}$-Ray Source facility in Durham, North Carolina, USA. Absorption cross sections were deduced for the magnetic and electric and dipole strength distributions separately for various intervals of excitation energy, including the strength of states in the unresolved quasicontinuum. The magnetic dipole strength distributions show structures resembling a resonance in the spin-flip region around an excitation energy of 8 MeV. The electric dipole strength distributions obtained from the present experiments are in agreement with the ones deduced from an earlier experiment using broad-band bremsstrahlung instead of a quasimonoenergetic beam. The experimental magnetic and electric dipole strength distributions are compared with phenomenological approximations and with predictions of a quasiparticle random phase approximation in a deformed basis.}, number={5}, journal={PHYSICAL REVIEW C}, author={Massarczyk, R. and Rusev, G. and Schwengner, R. and Doenau, F. and Bhatia, C. and Gooden, M. E. and Kelley, J. H. and Tonchev, A. P. and Tornow, W.}, year={2014}, month={Nov} } @article{massarczyk_schwengner_donau_frauendorf_anders_bemmerer_beyer_bhatia_birgersson_butterling_et al._2014, title={Nuclear Deformation and Neutron Excess as Competing Effects for Dipole Strength in the Pygmy Region}, volume={112}, number={7}, journal={Physical Review Letters}, author={Massarczyk, R. and Schwengner, R. and Donau, F. and Frauendorf, S. and Anders, M. and Bemmerer, D. and Beyer, R. and Bhatia, C. and Birgersson, E. and Butterling, M. and et al.}, year={2014} } @article{gooden_fallin_finch_kelley_howell_rusev_tonchev_tornow_stanislav_2014, title={Partial Cross Sections of Neutron-Induced Reactions on natCu at En = 6, 8, 10, 12, 14, and 16 MeV for 0νββ Background Studies}, volume={119}, ISSN={0090-3752}, url={http://dx.doi.org/10.1016/J.NDS.2014.08.034}, DOI={10.1016/J.NDS.2014.08.034}, abstractNote={Partial cross-section measurements of (n,n'γ) reactions on natCu were carried out at tunl using monoenergetic neutrons at six energies of En = 6, 8, 10, 12, 14, 16 MeV. These studies were performed to provide accurate cross-section data on materials abundant in experimental setups involving HPGe detectors used to search for rare events, like the neutrino-less double-beta decay of 76Ge. Spallation and (α,n) neutrons are expected to cause the largest source of external background in the energy region of interest. At tunl pulsed neutron beams were produced via the 2H(d,n)3He reaction and the deexcitation γ rays from the reaction natCu(n,xγ) were detected with clover HPGe detectors. Cross-section results for the strongest transtions in 63Cu and 65Cu will be reported, and will compared to model calculations and to data recently obtained at lanl with a white neutron beam.}, journal={Nuclear Data Sheets}, publisher={Elsevier BV}, author={Gooden, M.E. and Fallin, B.A. and Finch, S.W. and Kelley, J.H. and Howell, C.R. and Rusev, G. and Tonchev, A.P. and Tornow, W. and Stanislav, V.}, year={2014}, month={May}, pages={121–123} } @article{gooden_fallin_finch_kelley_howell_rusev_tonchev_tornow_stanislav_2014, title={Partial cross sections of neutron-induced reactions on Cu-nat at E-n=6, 8, 10, 12, 14, and 16 MeV for 0 nu beta beta background studies}, volume={119}, journal={Nuclear Data Sheets}, author={Gooden, M. E. and Fallin, B. A. and Finch, S. W. and Kelley, J. H. and Howell, C. R. and Rusev, G. and Tonchev, A. P. and Tornow, W. and Stanislav, V.}, year={2014}, pages={E121–123} } @article{isaak_savran_krtička_ahmed_beller_fiori_glorius_kelley_löher_pietralla_et al._2013, title={Constraining nuclear photon strength functions by the decay properties of photo-excited states}, volume={727}, ISSN={0370-2693}, url={http://dx.doi.org/10.1016/J.PHYSLETB.2013.10.040}, DOI={10.1016/J.PHYSLETB.2013.10.040}, abstractNote={A new approach for constraining the low-energy part of the electric dipole Photon Strength Function (E1-PSF) is presented. Experiments at the Darmstadt High-Intensity Photon Setup and the High Intensity γ→-Ray Source have been performed to investigate the decay properties of 130Te between 5.50 and 8.15 MeV excitation energy. In particular, the average γ-ray branching ratio to the ground state and the population intensity of low-lying excited states have been studied. A comparison to the statistical model shows that the latter is sensitive to the low-energy behavior of the E1-PSF, while the average ground state branching ratio cannot be described by the statistical model in the energy range between 5.5 and 6.5 MeV.}, number={4-5}, journal={Physics Letters B}, publisher={Elsevier BV}, author={Isaak, J. and Savran, D. and Krtička, M. and Ahmed, M.W. and Beller, J. and Fiori, E. and Glorius, J. and Kelley, J.H. and Löher, B. and Pietralla, N. and et al.}, year={2013}, month={Dec}, pages={361–365} } @article{raut_tonchev_rusev_tornow_iliadis_lugaro_buntain_goriely_kelley_schwengner_et al._2013, title={Cross-Section Measurements of the Kr-86(gamma, n) Reaction to Probe the s-Process Branching at Kr-85}, volume={111}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.111.112501}, abstractNote={For the first time, cross-section measurements were carried out for the 86Kr(γ, n) reaction in order to probe the s-process branching point nucleus 85Kr. The branching point nuclei in the s-process path are of importance in testing and constraining the nucleosynthesis models. Cross-section measurement for the photoneutron reaction on the neighbouring stable isotope is carried out to deduce the aforesaid neutron capture cross-section, as has been adopted in the present case of 85Kr branching point. The cross-section results from the 86Kr(γ, n) reaction were compared with the statistical model calculations using TALYS code.}, number={11}, journal={PHYSICAL REVIEW LETTERS}, author={Raut, R. and Tonchev, A. P. and Rusev, G. and Tornow, W. and Iliadis, C. and Lugaro, M. and Buntain, J. and Goriely, S. and Kelley, J. H. and Schwengner, R. and et al.}, year={2013}, month={Sep} } @article{scheck_ponomarev_aumann_beller_fritzsche_isaak_kelley_kwan_pietralla_raut_et al._2013, title={Decay pattern of the pygmy dipole resonance in Ni-60}, volume={87}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.87.051304}, abstractNote={The electric dipole strength distribution in 130Te has been investigated using the method of Nuclear Resonance Fluorescence. The experiments were performed at the Darmstadt High Intensity Photon Setup using bremsstrahlung as photon source and at the High Intensity ~γ-Ray Source, where quasi-monochromatic and polarized photon beams are provided. Average decay properties of 130Te below the neutron separation energy are determined. Comparing the experimental data to the predictions of the statistical model indicate, that nuclear structure effects play an important role even at sufficiently high excitation energies. Preliminary results will be presented.}, number={5}, journal={PHYSICAL REVIEW C}, author={Scheck, M. and Ponomarev, V. Yu. and Aumann, T. and Beller, J. and Fritzsche, M. and Isaak, J. and Kelley, J. H. and Kwan, E. and Pietralla, N. and Raut, R. and et al.}, year={2013}, month={May} } @article{goddard_cooper_werner_rusev_stevenson_rios_bernards_chakraborty_crider_glorius_et al._2013, title={Dipole response of Se-76 above 4 MeV}, volume={88}, number={6}, journal={Physical Review. C, Nuclear Physics}, author={Goddard, P. M. and Cooper, N. and Werner, V. and Rusev, G. and Stevenson, P. D. and Rios, A. and Bernards, C. and Chakraborty, A. and Crider, B. P. and Glorius, J. and et al.}, year={2013} } @article{rusev_tsoneva_doenau_frauendorf_schwengner_tonchev_adekola_hammond_kelley_kwan_et al._2013, title={Fine Structure of the Giant M1 Resonance in Zr-90}, volume={110}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.110.022503}, abstractNote={The M1 excitations in the nuclide 90Zr have been studied in a photon-scattering experiment with monoenergetic and linearly polarized beams from 7 to 11 MeV. More than 40 J(π)=1+ states have been identified from observed ground-state transitions, revealing the fine structure of the giant M1 resonance with a centroid energy of 9 MeV and a sum strength of 4.17(56) μ(N)(2). The result for the total M1 strength and its fragmentation are discussed in the framework of the three-phonon quasiparticle-phonon model.}, number={2}, journal={PHYSICAL REVIEW LETTERS}, author={Rusev, G. and Tsoneva, N. and Doenau, F. and Frauendorf, S. and Schwengner, R. and Tonchev, A. P. and Adekola, A. S. and Hammond, S. L. and Kelley, J. H. and Kwan, E. and et al.}, year={2013}, month={Jan} } @article{romig_beller_glorius_isaak_kelley_kwan_pietralla_ponomarev_sauerwein_savran_et al._2013, title={Low-lying dipole strength of the open-shell nucleus Mo-94}, volume={88}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.88.044331}, abstractNote={Thelow-lyingdipolestrengthoftheopen-shellnucleus 94 Mowasstudiedviathenuclearresonancefluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity γ-raySource(HIγS)facility.Intotal,83excitedstateswereidentified.Exploitingpolarizedquasi-monoenergetic photons at HIγS, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HIγS measurements at five energy settings. Mean branching ratios to the ground state and first excited 2 + state wereextractedfromthemeasurementswithquasi-monoenergeticphotonsandcomparedto γ-cascadesimulations withinthestatisticalmodel.Theexperimentallydeducedmeanbranchingratiosexhibitaresonance-likemaximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.}, number={4}, journal={PHYSICAL REVIEW C}, author={Romig, C. and Beller, J. and Glorius, J. and Isaak, J. and Kelley, J. H. and Kwan, E. and Pietralla, N. and Ponomarev, V. Yu and Sauerwein, A. and Savran, D. and et al.}, year={2013}, month={Oct} } @article{scheck_ponomarev_fritzsche_joubert_aumann_beller_isaak_kelley_kwan_pietralla_et al._2013, title={Photoresponse of Ni-60 below 10-MeV excitation energy: Evolution of dipole resonances in f p-shell nuclei near N = Z}, volume={88}, number={4}, journal={Physical Review. C, Nuclear Physics}, author={Scheck, M. and Ponomarev, V. Y. and Fritzsche, M. and Joubert, J. and Aumann, T. and Beller, J. and Isaak, J. and Kelley, J. H. and Kwan, E. and Pietralla, N. and et al.}, year={2013} } @article{schwengner_massarczyk_rusev_tsoneva_bemmerer_beyer_hannaske_junghans_kelley_kwan_et al._2013, title={Pygmy dipole strength in Kr-86 and systematics of N=50 isotones}, volume={87}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.87.024306}, abstractNote={The dipole strength of the $N=50$ nucleus ${}^{86}$Kr was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.9 and 11.2 MeV delivered by the linear accelerator ELBE as well as using quasimonoenergetic and linearly polarized $\ensuremath{\gamma}$ rays of 10 energies within the range from 4.7 to 9.3 MeV delivered by the HI$\ensuremath{\gamma}$S facility. A high-pressure gas target was used. We identified 39 levels up to an excitation energy of 10.1 MeV. Simulations of $\ensuremath{\gamma}$-ray cascades were performed to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section derived in this way up to the neutron-separation energy is combined with the photoabsorption cross section obtained from a $(\ensuremath{\gamma},n)$ experiment at HI$\ensuremath{\gamma}$S. The enhanced $E1$ strength found in the range from 6 to 10 MeV is compared with the ones in the $N$ $=$ 50 isotones ${}^{88}$Sr, ${}^{90}$Zr, and ${}^{92}$Mo and with predictions of calculations within the quasiparticle-phonon model.}, number={2}, journal={PHYSICAL REVIEW C}, author={Schwengner, R. and Massarczyk, R. and Rusev, G. and Tsoneva, N. and Bemmerer, D. and Beyer, R. and Hannaske, R. and Junghans, A. R. and Kelley, J. H. and Kwan, E. and et al.}, year={2013}, month={Feb} } @article{loher_derya_aumann_beller_cooper_duchene_endres_fiori_isaak_kelley_et al._2013, title={The high-efficiency gamma-ray spectroscopy setup gamma(3) at HI gamma S}, volume={723}, journal={Nuclear Instruments & Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors, and Associated Equipment}, author={Loher, B. and Derya, V. and Aumann, T. and Beller, J. and Cooper, N. and Duchene, M. and Endres, J. and Fiori, E. and Isaak, J. and Kelley, J. and et al.}, year={2013}, pages={136–142} } @article{hammond_adekola_angell_karwowski_kwan_rusev_tonchev_tornow_howell_kelley_2012, title={Dipole response of U-238 to polarized photons below the neutron separation energy}, volume={85}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.85.044302}, abstractNote={1) dipole strengths in nuclei[1]. Observation of dipole states are important because theycharacterize the various collective and single-particle nuclearexcitation modes, in particular, the scissors mode, the spin-flip mode, and the pygmy dipole resonance. These differentexcitation modes are prominent in various regions below ornear the neutron separation energy and represent importantnuclear structure phenomena. For}, number={4}, journal={PHYSICAL REVIEW C}, author={Hammond, S. L. and Adekola, A. S. and Angell, C. T. and Karwowski, H. J. and Kwan, E. and Rusev, G. and Tonchev, A. P. and Tornow, W. and Howell, C. R. and Kelley, J. H.}, year={2012}, month={Apr} } @article{massarczyk_schwengner_donau_litvinova_rusev_beyer_hannaske_junghans_kempe_kelley_et al._2012, title={Electromagnetic dipole strength of Ba-136 below the neutron separation energy}, volume={86}, number={1}, journal={Physical Review. C, Nuclear Physics}, author={Massarczyk, R. and Schwengner, R. and Donau, F. and Litvinova, E. and Rusev, G. and Beyer, R. and Hannaske, R. and Junghans, A. R. and Kempe, M. and Kelley, J. H. and et al.}, year={2012} } @article{kelley_kwan_purcell_sheu_weller_2012, title={Energy levels of light nuclei A=11}, volume={880}, ISSN={["1873-1554"]}, DOI={10.1016/j.nuclphysa.2012.01.010}, abstractNote={A review of evidence on the properties of the A=11 nuclei, with emphasis on material leading to information about the structure of the A=11 systems.}, journal={NUCLEAR PHYSICS A}, author={Kelley, J. H. and Kwan, E. and Purcell, J. E. and Sheu, C. G. and Weller, H. R.}, year={2012}, month={Apr}, pages={88–195} } @article{raut_tornow_ahmed_crowell_kelley_rusev_stave_tonchev_2012, title={Photodisintegration Cross Section of the Reaction He-4(gamma, p)H-3 between 22 and 30 MeV}, volume={108}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.108.042502}, abstractNote={The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together with a plastic scintillator paddle was employed for determining the incident photon flux. Our comprehensive data set follows the trend of the theoretical calculations of the Trento group very well, although our data are consistently lower in magnitude by about 5%. However, they differ significantly from the majority of the previous data, especially from the recent data of Shima et al. The latter data had put into question the validity of theoretical approaches used to calculate core-collapse supernova explosions and big-bang nucleosynthesis abundances of certain light nuclei.}, number={4}, journal={PHYSICAL REVIEW LETTERS}, author={Raut, R. and Tornow, W. and Ahmed, M. W. and Crowell, A. S. and Kelley, J. H. and Rusev, G. and Stave, S. C. and Tonchev, A. P.}, year={2012}, month={Jan} } @article{tornow_kelley_raut_rusev_tonchev_ahmed_crowell_stave_2012, title={Photodisintegration cross section of the reaction He-4(gamma,n)He-3 at the giant dipole resonance peak}, volume={85}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.85.061001}, abstractNote={The photodisintegration cross section of ${}^{4}$He into a neutron and helion was measured at incident photon energies of 27.0, 27.5, and 28.0 MeV. A high-pressure ${}^{4}$He-Xe gas scintillator served as target and detector while a pure Xe gas scintillator was used for background measurements. A NaI detector in combination with the standard HI$\ensuremath{\gamma}$S scintillator paddle system was employed for absolute photon-flux determination. Our data are in good agreement with the theoretical prediction of the Trento group and the recent data of Nilsson et al. [Phys. Rev. C 75, 014007 (2007)] but deviate considerably from the high-precision data of Shima et al. [Phys. Rev. C 72, 044004 (2005)].}, number={6}, journal={PHYSICAL REVIEW C}, author={Tornow, W. and Kelley, J. H. and Raut, R. and Rusev, G. and Tonchev, A. P. and Ahmed, M. W. and Crowell, A. S. and Stave, S. C.}, year={2012}, month={Jun} } @article{johnson_hagmann_hall_mcnabb_kelley_huibregtse_kwan_rusev_tonchev_2012, title={Searching for illicit materials using nuclear resonance fluorescence stimulated by narrow-band photon sources}, volume={285}, ISSN={["0168-583X"]}, DOI={10.1016/j.nimb.2012.05.029}, abstractNote={Abstract We report the results of an experimental study of the sensitivity of two distinct classes of systems that exploit nuclear resonance fluorescence (NRF) to search for illicit materials in containers. One class of systems is based on the direct detection of NRF photons emitted from isotopes of interest. The other class infers the presence of a particular isotope by observing the preferential attenuation of resonant photons in the incident beam. We developed a detailed analytical model for both approaches. We performed experiments to test the model using depleted uranium as a surrogate for illicit material and used tungsten as a random choice for shielding. We performed the experiments at Duke University’s High Intensity Gamma Source (HIGS). Using the methodology we detail in this paper one can use this model to estimate the performance of potential inspection systems in certifying containers as free of illicit materials and for detecting the presence of those same materials.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Johnson, M. S. and Hagmann, C. A. and Hall, J. M. and McNabb, D. P. and Kelley, J. H. and Huibregtse, C. and Kwan, E. and Rusev, G. and Tonchev, A. P.}, year={2012}, month={Aug}, pages={72–85} } @article{raut_crowell_fallin_howell_huibregtse_kelley_kawano_kwan_rusev_tonchev_et al._2011, title={Cross-section measurements of neutron-induced reactions on GaAs using monoenergetic beams from 7.5 to 15 MeV}, volume={83}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.83.044621}, abstractNote={Cross-section measurements for neutron-induced reactions on GaAs have been carried out at twelve different neutron energies from 7.5 to 15 MeV using the activation technique. The monoenergetic neutron beams were produced via the $^{2}\mathrm{H}$($d,n$)$^{3}\mathrm{He}$ reaction. GaAs samples were activated along with Au and Al monitor foils to determine the incident neutron flux. The activities induced by the reaction products were measured using high-resolution $\ensuremath{\gamma}$-ray spectroscopy. Cross sections for five reaction channels, viz., $^{69}\mathrm{Ga}$($n,2n$)$^{68}\mathrm{Ga}$, $^{69}\mathrm{Ga}$($n,p$)$^{69}\mathrm{Zn}$${}^{m}$, $^{71}\mathrm{Ga}$($n,p$)$^{71}\mathrm{Zn}$${}^{m}$, $^{75}\mathrm{As}$($n,2n$)$^{74}\mathrm{As}$, and $^{75}\mathrm{As}$($n,p$)$^{75}\mathrm{Ge}$, are reported. The results are compared with the previous measurements and available data evaluations. Statistical-model calculations, based on the Hauser-Feshbach formalism, have been carried out using the TALYS and the COH3 codes and are compared with the experimental results.}, number={4}, journal={PHYSICAL REVIEW C}, author={Raut, R. and Crowell, A. S. and Fallin, B. and Howell, C. R. and Huibregtse, C. and Kelley, J. H. and Kawano, T. and Kwan, E. and Rusev, G. and Tonchev, A. P. and et al.}, year={2011}, month={Apr} } @article{adekola_angell_hammond_hill_howell_karwowski_kelley_kwan_2011, title={Discovery of low-lying E1 and M1 strengths in Th-232}, volume={83}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.83.034615}, abstractNote={Properties of low-energy dipole states in {sup 232}Th have been investigated with the nuclear resonance fluorescence technique. The present work used monoenergetic {gamma}-ray beams at energies of 2-4 MeV from the high-intensity {gamma}-ray source at Triangle Universities Nuclear Laboratory. Over 40 transitions corresponding to deexcitation to the ground state and first excited state were observed for the first time. Excitation energies, integrated cross sections, decay widths, branching ratios, and transition strengths for those states in {sup 232}Th were determined and compared with quasiparticle random-phase-approximation calculations. A large number of E1 transitions were observed for the first time in actinide nuclei with summed strength of 3.28(69)x10{sup -3} e{sup 2} fm{sup 2}. The observed summed M1 strength of 4.26(63){mu}{sub N}{sup 2} is in good agreement with the other actinides and with the systematics of the scissors mode in deformed rare-earth nuclei.}, number={3}, journal={PHYSICAL REVIEW C}, author={Adekola, A. S. and Angell, C. T. and Hammond, S. L. and Hill, A. and Howell, C. R. and Karwowski, H. J. and Kelley, J. H. and Kwan, E.}, year={2011}, month={Mar} } @article{kwan_rusev_adekola_doenau_hammond_howell_karwowski_kelley_pedroni_raut_et al._2011, title={Discrete deexcitations in U-235 below 3 MeV from nuclear resonance fluorescence}, volume={83}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.83.041601}, abstractNote={Gamma-ray transitions in {sup 235}U were measured using the ({gamma},{gamma}{sup '}) reaction below 3 MeV. The nuclear-resonance-fluorescence experiment was carried out at the High-Intensity {gamma}-ray Source facility using nearly monoenergetic and circularly polarized photon beams. More than 20 transitions corresponding to deexcitations to the ground state and low-lying levels in {sup 235}U were observed. The integrated cross sections to the excited levels and intensities of branching transitions were deduced. The experimental results are compared with predictions from a quasiparticle random-phase approximation in a deformed basis.}, number={4}, journal={PHYSICAL REVIEW C}, author={Kwan, E. and Rusev, G. and Adekola, A. S. and Doenau, F. and Hammond, S. L. and Howell, C. R. and Karwowski, H. J. and Kelley, J. H. and Pedroni, R. S. and Raut, R. and et al.}, year={2011}, month={Apr} } @article{isaak_savran_fritzsche_galaviz_hartmann_kamerdzhiev_kelley_kwan_pietralla_romig_et al._2011, title={Investigation of low-lying electric dipole strength in the semimagic nucleus Ca-44}, volume={83}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.83.034304}, abstractNote={The dipole-strength distribution in the semimagic nucleus {sup 44}Ca has been measured up to 10 MeV excitation energy in photon-scattering experiments using bremsstrahlung and monoenergetic 100% linearly polarized photon beams. The combination of both measurements allows a clear determination of spin and parity quantum numbers of the excited states as well as absolute cross sections and transition probabilities. The results show that the majority of the dipole strength in {sup 44}Ca below 10 MeV is due to E1 transitions while M1 strength plays only a minor role. The experimental results are compared to the strength in the neighboring doubly magic nuclei {sup 40,48}Ca and to microscopic calculations within the extended theory of finite Fermi systems in order to investigate the evolution of the low-lying E1 strength in this isotopic chain. Both, experiment and calculations, show a nontrivial dependence of the total E1 strength as a function of the neutron number.}, number={3}, journal={PHYSICAL REVIEW C}, author={Isaak, J. and Savran, D. and Fritzsche, M. and Galaviz, D. and Hartmann, T. and Kamerdzhiev, S. and Kelley, J. H. and Kwan, E. and Pietralla, N. and Romig, C. and et al.}, year={2011}, month={Mar} } @article{tornow_karwowski_kelley_raut_rusev_stave_tonchev_deltuva_fonseca_marcucci_et al._2011, title={Two-body photodisintegration of He-3 between 7 and 16 MeV}, volume={702}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2011.06.080}, abstractNote={Abstract A comprehensive data set is reported for the two-body photodisintegration cross section of 3He using mono-energetic photon beams at eleven energies between 7.0 and 16.0 MeV. A He 3 + Xe high-pressure gas scintillator served as target and detector. Although our data are in much better agreement with our state-of-the-art theoretical calculations than the majority of the previous data, these calculations underpredict the new data by about 10%. This disagreement suggests an incomplete understanding of the dynamics of the three-nucleon system and its response to electromagnetic probes.}, number={2-3}, journal={PHYSICS LETTERS B}, author={Tornow, W. and Karwowski, H. J. and Kelley, J. H. and Raut, R. and Rusev, G. and Stave, S. C. and Tonchev, A. P. and Deltuva, A. and Fonseca, A. C. and Marcucci, L. E. and et al.}, year={2011}, month={Aug}, pages={121–126} } @article{purcell_kelley_kwan_sheu_weller_2010, title={Energy levels of light nuclei A=3}, volume={848}, ISSN={["1873-1554"]}, DOI={10.1016/j.nuclphysa.2010.08.012}, abstractNote={A compilation of experimental and theoretical information is presented on the mass 3 systems 3n, 3H, 3He and 3p. Emphasis is on advances since the previous evaluation Tilley et al. (1987) [1987TI07] such as, (1) detailed calculations of the vector and tensor analyzing powers for neutron and proton scattering by deuterium which led to the discovery of the still unresolved analyzing power puzzle, (2) the wide spread use of polarized 3He targets which allowed for the experimental study of sum rules among other things and (3) the ability to include the Coulomb interaction in three-body calculations. As stated in the 1987 evaluation and is still the case, there is no firm evidence for either excited states of 3H or 3He nuclei or for the existence of the trineutron or triproton.}, number={1-2}, journal={NUCLEAR PHYSICS A}, author={Purcell, J. E. and Kelley, J. H. and Kwan, E. and Sheu, C. G. and Weller, H. R.}, year={2010}, month={Dec}, pages={1–74} } @article{carson_iliadis_cesaratto_champagne_downen_ivanovic_kelley_longland_newton_rusev_et al._2010, title={Ratio of germanium detector peak efficiencies at photon energies of 4.4 and 11.7 MeV: Experiment versus simulation}, volume={618}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2010.02.128}, abstractNote={Full-energy peak efficiencies of germanium detectors are frequently investigated at γ-ray energies below 4 MeV using calibrated radioactive sources, while very accurate peak efficiencies for higher photon energies are essentially non-existent. Peak efficiencies in the energy range of Eγ=4–12MeV are crucial for a number of applications, including nuclear astrophysics measurements of fusion reactions and resonance fluorescence experiments. We report on a novel method, using the 163 keV resonance in the B11(p,γ)C12 reaction, of measuring accurately the ratio of full-energy peak efficiencies at 4.44 and 11.66 MeV. We derive this ratio for three different detector-target distances (3, 12 and 26 cm) directly from measured peak intensities and demonstrate that corrections are small (γ-ray branching ratios, angular correlations, coincidence summing). Our measured full-energy peak efficiency ratios have a precision of 1.4–1.6%. Another important goal of our study was to determine to what precision full-energy peak efficiencies at high γ-ray energies can be predicted using the simulation codes Geant3 and Geant4. We imaged our detector using computed tomography and radiographs in order to extract reliable detector crystal dimensions. Based on these results, extensive computer simulations are performed. We find that the simulation results agree with the measured peak efficiency ratios within an uncertainty of 1.6% for Geant4 and 2.6% for Geant3. Our results are useful for assigning uncertainties when peak efficiencies are extrapolated from low energy data to high energies based on simulations only.}, number={1-3}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, publisher={Elsevier BV}, author={Carson, Spencer and Iliadis, Christian and Cesaratto, John and Champagne, Art and Downen, Lori and Ivanovic, Marija and Kelley, John and Longland, Richard and Newton, Joseph R. and Rusev, Gencho and et al.}, year={2010}, month={Jun}, pages={190–198} } @article{tonchev_hammond_kelley_kwan_lenske_rusev_tornow_tsoneva_2010, title={Spectral Structure of the Pygmy Dipole Resonance}, volume={104}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.104.072501}, abstractNote={High-sensitivity studies of E1 and M1 transitions observed in the reaction 138Ba(gamma,gamma{'}) at energies below the one-neutron separation energy have been performed using the nearly monoenergetic and 100% linearly polarized photon beams of the HIgammaS facility. The electric dipole character of the so-called "pygmy" dipole resonance was experimentally verified for excitations from 4.0 to 8.6 MeV. The fine structure of the M1 "spin-flip" mode was observed for the first time in N=82 nuclei.}, number={7}, journal={PHYSICAL REVIEW LETTERS}, author={Tonchev, A. P. and Hammond, S. L. and Kelley, J. H. and Kwan, E. and Lenske, H. and Rusev, G. and Tornow, W. and Tsoneva, N.}, year={2010}, month={Feb} } @article{hutcheson_angell_becker_crowell_dashdorj_fallin_fotiades_howell_karwowski_kawano_et al._2009, title={Cross sections for U-238(n,n(')gamma) and U-238(n,2n gamma) reactions at incident neutron energies between 5 and 14 MeV}, volume={80}, ISSN={["2469-9993"]}, DOI={10.1103/physrevc.80.014603}, abstractNote={Precision measurements of {sup 238}U(n,n{sup '}{gamma}) and {sup 238}U(n,2n{gamma}) partial cross sections have been performed at Triangle Universities Nuclear Laboratory (TUNL) to improve crucial data needed for testing nuclear reaction models in the actinide mass region. A pulsed and monoenergetic neutron beam was used in combination with high-resolution {gamma}-ray spectroscopy to obtain partial cross sections for incident neutron energies between 5 and 14 MeV. {gamma}-ray yields were measured with high-purity germanium clover and planar detectors. Measured partial cross-section data are compared with previous results using white and monoenergetic neutron beams and calculations from the GNASH and TALYS Hauser-Feshbach statistical-model codes. Present experimental results are in fair to good agreement with most of the existing data for the {sup 238}U(n,n{sup '}{gamma}) reaction. However, significant discrepancies are observed for the {sup 238}U(n,2n{gamma}) reaction.}, number={1}, journal={PHYSICAL REVIEW C}, author={Hutcheson, A. and Angell, C. and Becker, J. A. and Crowell, A. S. and Dashdorj, D. and Fallin, B. and Fotiades, N. and Howell, C. R. and Karwowski, H. J. and Kawano, T. and et al.}, year={2009}, month={Jul} } @article{hagmann_hall_johnson_mcnabb_kelley_huibregtse_kwan_rusev_tonchev_2009, title={Transmission-based detection of nuclides with nuclear resonance fluorescence using a quasimonoenergetic photon source}, volume={106}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3238328}, DOI={10.1063/1.3238328}, abstractNote={We provide a detailed experimental validation of the concept of transmission-based isotope detection. The dominant background processes in this class of systems were measured by studying the detection of U238 with a quasimonochromatic (ΔE∕E∼3%) photon beam. A notch develops in the spectrum transmitted through our test objects due to the preferential attenuation of photons with an energy that resonantly excites a bound nuclear state in U238 near 2 MeV. The notch was measured downstream of our test objects by means of resonant photon scattering from a secondary U238 target. The dominant backgrounds measured in the notch detector due to radioactive decay and elastic scattering of the transmitted beam are presented. Processes that refill the notch with off-resonance photons will obscure the signal and result in a higher probability of false negatives. A measurement of the refill process produced a null result, and we report an upper limit on the magnitude of the notch fill factor.}, number={8}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Hagmann, C. A. and Hall, J. M. and Johnson, M. S. and McNabb, D. P. and Kelley, J. H. and Huibregtse, C. and Kwan, E. and Rusev, G. and Tonchev, A. P.}, year={2009}, month={Oct}, pages={084901} } @article{elhami_orce_scheck_mukhopadhyay_choudry_mcellistrem_yates_angell_boswell_fallin_et al._2008, title={Experimental study of the low-lying structure of Zr-94 with the (n, n ' gamma) reaction}, volume={78}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.78.064303}, abstractNote={The low-lying structure of {sub 40}{sup 94}Zr was studied with the (n,n{sup '}{gamma}) reaction, and a level scheme was established based on excitation function and {gamma}{gamma} coincidence measurements. Branching ratios, multipole mixing ratios, and spin assignments were determined from angular distribution measurements. Lifetimes of levels up to 3.4 MeV were measured by the Doppler-shift attenuation method, and for many transitions the reduced transition probabilities were determined. In addition to the anomalous 2{sub 2}{sup +} state, which has a larger B(E2;2{sub 2}{sup +}{yields}0{sub 1}{sup +}) value than the B(E2;2{sub 1}{sup +}{yields}0{sub 1}{sup +}), the experimental results revealed interesting and unusual properties of the low-lying states in {sup 94}Zr. In a simple interpretation, the excited states are classified in two distinct categories, i.e., those populating the 2{sub 2}{sup +} state and those decaying to the 2{sub 1}{sup +} state.}, number={6}, journal={PHYSICAL REVIEW C}, author={Elhami, E. and Orce, J. N. and Scheck, M. and Mukhopadhyay, S. and Choudry, S. N. and McEllistrem, M. T. and Yates, S. W. and Angell, C. and Boswell, M. and Fallin, B. and et al.}, year={2008}, month={Dec} } @article{tonchev_angell_boswell_crowell_fallin_hammond_howell_hutcheson_karwowski_kelley_et al._2008, title={Measurement of the Am-241(n, 2n) reaction cross section from 7.6 MeV to 14.5 MeV}, volume={77}, number={5}, journal={Physical Review. C, Nuclear Physics}, author={Tonchev, A. P. and Angell, C. T. and Boswell, M. and Crowell, A. S. and Fallin, B. and Hammond, S. and Howell, C. R. and Hutcheson, A. and Karwowski, H. J. and Kelley, J. H. and et al.}, year={2008} } @inproceedings{vieira_jandel_bredeweg_bond_clement_couture_haight_o'donnell_reifarth_rundberg_et al._2007, title={Neutron capture and (n,2n) measurements on 241Am}, url={http://dx.doi.org/10.1051/NDATA:07636}, DOI={10.1051/NDATA:07636}, abstractNote={We report on a set of neutron-induced reaction measurements on {sup 241}Am which are important for nuclear forensics and advanced nuclear reactor design. Neutron capture measurements have been performed on the DANCE detector array at the Los Alamos Neutron Scattering CEnter (LANSCE). In general, good agreement is found with the most recent data evaluations up to an incident neutron energy of {approx} 300 keV where background limits the measurement. Using mono-energetic neutrons produced in the {sup 2}H(d,n){sup 3}He reaction at Triangle University Nuclear Laboratory (TUNL), we have measured the {sup 241}Am(n,2n) excitation function from threshold (6.7 MeV) to 14.5 MeV using the activation method. Good agreement is found with previous measurements, with the exception of the three data points reported by Perdikakis et al. around 11 MeV, where we obtain a much lower cross section that is more consistent with theoretical estimates.}, booktitle={ND2007}, publisher={EDP Sciences}, author={Vieira, D. J. and Jandel, M. and Bredeweg, T. A. and Bond, E. M. and Clement, R. R. and Couture, A. and Haight, R. C. and O'Donnell, J. M. and Reifarth, R. and Rundberg, R. S. and et al.}, year={2007} } @article{hutcheson_angell_becker_boswell_crowell_dashdorj_fallin_fotiades_howell_karwowski_et al._2007, title={Pulsed and monoenergetic beams for neutron cross-section measurements using activation and scattering techniques at Triangle Universities Nuclear Laboratory}, volume={261}, ISSN={0168-583X}, url={http://dx.doi.org/10.1016/j.nimb.2007.04.097}, DOI={10.1016/j.nimb.2007.04.097}, abstractNote={In support of the Stewardship Science Academic Alliances initiative, an experimental program has been developed at Triangle Universities Nuclear Laboratory (TUNL) to measure (n,xn) cross-sections with both in-beam and activation techniques with the goal of improving the partial cross-section database for the NNSA Stockpile Stewardship Program. First experimental efforts include excitation function measurements on 235,238U and 241Am using pulsed and monoenergetic neutron beams with En = 5–15 MeV. Neutron-induced partial cross-sections were measured by detecting prompt γ rays from the residual nuclei using various combinations of clover and planar HPGe detectors in the TUNL shielded neutron source area. Complimentary activation measurements using DC neutron beams have also been performed in open geometry in our second target area. The neutron-induced activities were measured in the TUNL low-background counting area. In this presentation, we include detailed information about the irradiation procedures and facilities and preliminary data on first measurements using this capability.}, number={1-2}, journal={Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms}, publisher={Elsevier BV}, author={Hutcheson, A. and Angell, C.T. and Becker, J.A. and Boswell, M. and Crowell, A.S. and Dashdorj, D. and Fallin, B. and Fotiades, N. and Howell, C.R. and Karwowski, H.J. and et al.}, year={2007}, month={Aug}, pages={369–372} } @article{hadjidakis_guidal_garçon_laget_smith_vanderhaeghen_adams_ambrozewicz_anciant_anghinolfi_et al._2005, title={Exclusive ρ0 meson electroproduction from hydrogen at CLAS}, volume={605}, ISSN={0370-2693}, url={http://dx.doi.org/10.1016/j.physletb.2004.11.019}, DOI={10.1016/j.physletb.2004.11.019}, abstractNote={The longitudinal and transverse components of the cross section for the $e p\to e^\prime p \rho^0$ reaction were measured in Hall B at Jefferson Laboratory using the CLAS detector. The data were taken with a 4.247 GeV electron beam and were analyzed in a range of $x_B$ from 0.2 to 0.6 and of $Q^2$ from 1.5 to 3.0 GeV$^2$. The data are compared to a Regge model based on effective hadronic degrees of freedom and to a calculation based on Generalized Parton Distributions. It is found that the transverse part of the cross section is well described by the former approach while the longitudinal part can be reproduced by the latter.}, number={3-4}, journal={Physics Letters B}, publisher={Elsevier BV}, author={Hadjidakis, C. and Guidal, M. and Garçon, M. and Laget, J.-M. and Smith, E.S. and Vanderhaeghen, M. and Adams, G. and Ambrozewicz, P. and Anciant, E. and Anghinolfi, M. and et al.}, year={2005}, month={Jan}, pages={256–264} } @article{protopopescu_hersman_holtrop_adams_ambrozewicz_anciant_anghinolfi_asavapibhop_asryan_audit_et al._2005, title={Survey of asymmetries in semi-exclusive electron scattering on 4He and 12C}, volume={748}, ISSN={0375-9474}, url={http://dx.doi.org/10.1016/j.nuclphysa.2004.11.009}, DOI={10.1016/j.nuclphysa.2004.11.009}, abstractNote={Single spin azimuthal asymmetries A_LT' were measured at Jefferson Lab using 2.2 and 4.4 GeV longitudinally polarized electrons incident on He4 and C12 targets in the CLAS detector. A_LT' is related to the imaginary part of the longitudinal-transverse interference and in quasifree nucleon knockout it provides an unambiguous signature for final state interactions (FSI). Experimental values of A_LT' were found to be below 5%, typically |A_LT'| < 3% for data with good statistical precision. Optical Model in Eikonal Approximation (OMEA) and Relativistic Multiple-Scattering Glauber Approximation (RMSGA) calculations are shown to be consistent with the measured asymmetries.}, number={3-4}, journal={Nuclear Physics A}, publisher={Elsevier BV}, author={Protopopescu, D. and Hersman, F.W. and Holtrop, M. and Adams, G. and Ambrozewicz, P. and Anciant, E. and Anghinolfi, M. and Asavapibhop, B. and Asryan, G. and Audit, G. and et al.}, year={2005}, month={Feb}, pages={357–373} } @article{tonchev_boswell_howell_karwowski_kelley_tornow_wu_2005, title={The high intensity gamma-ray source (HI gamma S) and recent results}, volume={241}, ISSN={["1872-9584"]}, DOI={10.1016/j.nimb.2005.07.080}, abstractNote={The high intensity γ-ray source (HIγS) utilizes intra-cavity backscattering of free electron laser photons from the Duke electron storage ring to produce a unique monoenergetic beam of high-flux γ-rays with high polarization and selectable energy resolution. At present, γ-ray beams with energies from 2 to 58 MeV are available with intensities as high as 105–5 × 106 γ/s, energy spreads of 3% or better, and nearly 100% linear polarization. The quality and intensity of the γ-ray beams at HIγS are responsible for the unprecedented performance of this facility in a broad range of research programs in nuclear structure, nuclear astrophysics and nuclear applications. Recent results from excitation of isomeric states in (γ, n) reactions and parity assignments of dipole states determined via the (γ, γ′) reaction are presented.}, number={1-4}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Tonchev, AP and Boswell, M and Howell, CR and Karwowski, HJ and Kelley, JH and Tornow, W and Wu, YK}, year={2005}, month={Dec}, pages={170–175} } @article{prior_spraker_amthor_keeter_nelson_sabourov_sabourov_tonchev_ahmed_kelley_et al._2004, title={Energy dependence of the astrophysical S factor for the Li-6(p, gamma)Be-7 reaction}, volume={70}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.70.055801}, abstractNote={Polarized proton beams with energies from 80 to 130 keV have been used to determine the slope of the astrophysical S factor for the {sup 6}Li(p,{gamma}{sub 0}){sup 7}Be and {sup 6}Li(p,{gamma}{sub 1}){sup 7}Be reactions. The slope was determined from the relative yields at five incident proton energies. The slope of the S factor was found to be negative. The analyzing power measurements indicate that the reaction proceeds predominately by s-wave capture. The negative slope does not appear to be due to low-binding-energy effects, the effects of nearby resonances, or electron screening of the nuclei. A resonating group model calculation demonstrates a new mechanism for producing a negative slope at astrophysically relevant energies in radiative capture reactions.}, number={5}, journal={PHYSICAL REVIEW C}, author={Prior, RM and Spraker, MC and Amthor, AM and Keeter, KJ and Nelson, SO and Sabourov, A and Sabourov, K and Tonchev, A and Ahmed, M and Kelley, JH and et al.}, year={2004}, month={Nov} } @misc{tilley_kelley_godwin_millener_purcell_sheu_weller_2004, title={Energy levels of light nuclei A=8, 9, 10}, volume={745}, ISSN={["1873-1554"]}, DOI={10.1016/j.nuclphysa.2004.09.059}, abstractNote={A review of the evidence on the properties of the nuclei A=8, 9 and 10, with emphasis on material leading to information about the structure of the A=8,9,10 systems.}, number={3-4}, journal={NUCLEAR PHYSICS A}, author={Tilley, DR and Kelley, JH and Godwin, JL and Millener, DJ and Purcell, JE and Sheu, CG and Weller, HR}, year={2004}, month={Dec}, pages={155–362} } @article{tornow_czakon_howell_hutcheson_kelley_litvinenko_mikhailov_pinayev_weisel_witala_2003, title={Analyzing power for the photodisintegration of the deuteron between E-gamma=2.4 and 4.0 MeV}, volume={18}, ISSN={["0217-7323"]}, DOI={10.1142/S021773230301034X}, abstractNote={ The photon analyzing power for the photodisintegration of the deuteron was measured for seven gamma-ray energies between 2.39 and 4.05 MeV using the linearly polarized gamma-ray beam of the High-Intensity Gamma-ray Source at the Duke Free-Electron Laser Laboratory. The data provide a stringent test of theoretical calculations for the inverse reaction, the neutron-proton radiative capture reaction at energies important for Big-Bang nucleosynthesis. Our data are in excellent agreement with potential model and effective field theory calculations. }, number={2-6}, journal={MODERN PHYSICS LETTERS A}, author={Tornow, W and Czakon, NG and Howell, CR and Hutcheson, A and Kelley, JH and Litvinenko, VN and Mikhailov, S and Pinayev, IV and Weisel, GJ and Witala, H}, year={2003}, month={Feb}, pages={282–285} } @article{tornow_czakon_howell_hutcheson_kelley_litvinenko_mikhailov_pinayev_weisel_witala_2003, title={Low-energy photodisintegration of the deuteron and Big-Bang nucleosynthesis}, volume={574}, number={02-Jan}, journal={Physics Letters. B}, author={Tornow, W. and Czakon, N. G. and Howell, C. R. and Hutcheson, A. and Kelley, J. H. and Litvinenko, V. N. and Mikhailov, S. F. and Pinayev, I. V. and Weisel, G. J. and Witala, H.}, year={2003}, pages={13-} } @article{tonchev_nelson_sabourov_crowley_joshi_weller_kelley_prior_spraker_kalantar-nayestanaki_2003, title={The B-10((p)over-right-arrow, gamma)C-11 reaction at astrophysically relevant energies}, volume={68}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.68.045803}, abstractNote={The B-10(, gamma)C-11 reaction was studied by detecting the gamma-rays produced when 100, 130-, and 160-keV polarized protons were stopped in a thick B-10 target. Polarized and unpolarized incident beams were used to measure the cross section and vector analyzing power as a function of angle and energy for capture to the ground (J(pi)=3/2(-)), the second (E=4319 keV, J(pi)=5/2(-)), and the fifth (E=6478 keV, J(pi)=7/2(-)) excited states of C-11. The data were analyzed to obtain the amplitudes and phases of the contributing transition-matrix elements at each measured energy for all three transitions. Values of the astrophysical S factors were obtained from the cross section data and are compared to previous results. A direct capture plus resonance model calculation was performed in an attempt to account for all measured quantities. It was found that the large (similar to32%) value of A(y)(90degrees) observed in the case of capture to the ground state could be accounted for by including the subthreshold resonance at 8420 keV.}, number={4}, journal={PHYSICAL REVIEW C}, author={Tonchev, AP and Nelson, SO and Sabourov, K and Crowley, BT and Joshi, K and Weller, HR and Kelley, JH and Prior, RM and Spraker, M and Kalantar-Nayestanaki, N}, year={2003}, month={Oct} } @misc{tilley_cheves_godwin_hale_hofmann_kelley_sheu_weller_2002, title={Energy levels of light nuclei A=5, 6, 7}, volume={708}, ISSN={["1873-1554"]}, DOI={10.1016/S0375-9474(02)00597-3}, abstractNote={A review of the evidence on the properties of the nuclei A=5, 6 and 7, with emphasis on material leading to information about the structure of the A=5, 6, 7 systems. (References closed 23 August 2001.)}, number={1-2}, journal={NUCLEAR PHYSICS A}, author={Tilley, DR and Cheves, CM and Godwin, JL and Hale, GM and Hofmann, HM and Kelley, JH and Sheu, CG and Weller, HR}, year={2002}, month={Sep}, pages={3–163} } @article{canon_nelson_sabourov_wulf_weller_prior_spraker_kelley_tilley_2002, title={H-3((p)over-right-arrow,gamma)He-4 reaction below E-p=80 keV}, volume={65}, number={4}, journal={Physical Review. C, Nuclear Physics}, author={Canon, R. S. and Nelson, S. O. and Sabourov, K. and Wulf, E. and Weller, H. R. and Prior, R. M. and Spraker, M. and Kelley, J. H. and Tilley, D. R.}, year={2002}, pages={044008–1} } @article{nesaraja_brune_crowley_kelley_nelson_prior_sabourov_tilley_tonchev_weller_2001, title={Ratio of S factors for (p,gamma) reactions on C-12 and C-13 at astrophysically relevant energies - art. no. 065804}, volume={6406}, number={6}, journal={Physical Review. C, Nuclear Physics}, author={Nesaraja, C. D. and Brune, C. R. and Crowley, B. T. and Kelley, J. H. and Nelson, S. O. and Prior, R. M. and Sabourov, K. and Tilley, D. R. and Tonchev, A. and Weller, H. R.}, year={2001}, pages={5804-} } @article{roskowski_miraglia_preble_einfeldt_stiles_davis_schuck_grober_schwarz_2001, title={Strain and dislocation reduction in maskless pendeo-epitaxy GaN thin films}, volume={188}, DOI={10.1002/1521-396x(200112)188:2<729::aid-pssa729>3.0.co;2-w}, abstractNote={Measurement of strain in GaN films grown via pendeo-epitaxy (PE) indicates that the overgrowth, or wing, material is crystallographically relaxed. An increase of ≈0.02% in the c-axis lattice parameter of the wing material was measured via high-resolution X-ray diffraction (HRXRD); additional evidence for this increase was indicated by an upward shift of the E2 Raman line frequency. Atomic force microscopy studies revealed a reduction in the density of mixed-type dislocations in the wing. A reduction in screw-type dislocations in the wings with respect to the stripes is indicated by a reduction in HRXRD rocking curve FWHM of the (0002) reflections from 646 to 354 arcsec. The off-axis FWHM of the wing area was 126 arcsec compared to 296 arcsec for the stripe indicating a reduction in the edge-type dislocations as well. Pendeo-epitaxy growth of wings off the (110) surface of a GaN stripe produced a material that is crystallographically relaxed, contains fewer defects compared to the stripe and is atomically smooth on the (110) surface.}, number={2}, journal={Physica Status Solidi. A, Applications and Materials Science}, author={Roskowski, A. M. and Miraglia, P. Q. and Preble, E. A. and Einfeldt, S. and Stiles, T. and Davis, R. F. and Schuck, J. and Grober, R. and Schwarz, U.}, year={2001}, pages={729–732} } @article{nelson_wulf_kelley_weller_2000, title={Evaluations of thermonuclear proton capture reaction rates for H-2, Li-7, Be-9, and B-11}, volume={679}, ISSN={["1873-1554"]}, DOI={10.1016/S0375-9474(00)00341-9}, abstractNote={Recent measurements and analyses of proton induced radiative-capture reactions in the vicinity of Ep=100 keV performed at the Triangle Universities Nuclear Laboratory are used to calculate the thermonuclear reaction rates of relevance in astrophysical plasmas for the reactions: D(p, γ )3 He, 7 Li(p, γ0,1 )8 Be, 9 Be(p, γ0,1,2,3 )10 B, and 11 B(p, γ0,1 )12 C. Higher energy data from previous measurements were included when possible. The Maxwellian-averaged reaction rates, obtained using numerical integration techniques, are presented in tabular form as a function of temperature. Capture to the ground and excited states are treated separately, thus allowing the determination of inverse reaction rates for specified target states. The high temperature cut-offs of the reaction rate calculations are discussed. The results are compared to those presented in the recent NACRE compilation, where appropriate, and new analytical approximations for the total reaction rates are presented in a standard form.}, number={2}, journal={NUCLEAR PHYSICS A}, author={Nelson, SO and Wulf, EA and Kelley, JH and Weller, HR}, year={2000}, month={Nov}, pages={199–211} }