@inproceedings{hallen_willitsford_neely_chadwick_philbrick_2016, title={Atmospheric absorption versus deep ultraviolet (pre-)resonance in Raman LIDAR measurements}, volume={9832}, booktitle={Laser radar technology and applications xxi}, author={Hallen, H. D. and Willitsford, A. H. and Neely, R. R. and Chadwick, C. T. and Philbrick, C. R.}, year={2016} }
 @article{willitsford_chadwick_kurtz_philbrick_hallen_2016, title={Resonance-Enhanced Raman Scattering of Ring-Involved Vibrational Modes in the B-1(2u) Absorption Band of Benzene, Including the Kekule Vibrational Modes nu(9) and nu(10)}, volume={120}, ISSN={["1520-5215"]}, url={http://dx.doi.org/10.1021/acs.jpca.5b08159}, DOI={10.1021/acs.jpca.5b08159}, abstractNote={Resonance Raman spectroscopy provides much stronger Raman signal levels than its off-resonant counterpart and adds selectivity by excitation tuning. Raman preresonance of benzene has been well studied. On-resonance studies, especially at phonon-allowed absorptions, have received less attention. In this case, we observe resonance of many of the vibration modes associated motion of the carbons in the ring while tuning over the (1)B2u absorption, including the related ν9 (CC stretch Herzberg notation, ν14 Wilson notation) and ν10 (CH-parallel bend Herzberg notation, ν15 Wilson notation) vibrational modes along with the ν2 (CC-stretch or ring-breathing Herzberg notation, ν1 Wilson notation) mode and multiples of the ν18 (CCC-parallel bend Herzberg notation, ν6 Wilson notation) vibrational mode. The ring-breathing mode is found to mix with the b2u modes creating higher frequency composites. Through the use of an optical parametric oscillator (OPO) to tune through the (1)B2u absorption band of liquid benzene, a stiffening (increase in energy) of the vibrational modes is observed as the excitation wavelength nears the (1)B2u absorption peak of the isolated molecule (vapor) phase. The strongest resonance amplitude observed is in the 2 × ν18 (e2g) mode, with nearly twice the intensity of the ring-breathing mode, ν2. Several overtones and combination modes, especially with ν2 (a1g), are also observed to resonate. Raman resonances on phonon-allowed excitations are narrow and permit the measurement of vibrations not Raman-active in the ground state.}, number={4}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Willitsford, Adam H. and Chadwick, C. Todd and Kurtz, Stewart and Philbrick, C. Russell and Hallen, Hans}, year={2016}, month={Feb}, pages={503–506} }
 @article{chadwick_willitsford_philbrick_hallen_2015, title={Deep ultraviolet Raman spectroscopy: A resonance-absorption trade-off illustrated by diluted liquid benzene}, volume={118}, number={24}, journal={Journal of Applied Physics}, author={Chadwick, C. T. and Willitsford, A. H. and Philbrick, C. R. and Hallen, H. D.}, year={2015} }
 @inproceedings{philbrick_hallen_2015, title={Lidar investigations of atmospheric dynamics}, volume={9612}, booktitle={Lidar remote sensing for environmental monitoring xv}, author={Philbrick, C. R. and Hallen, H. D.}, year={2015} }
 @inproceedings{hallen_willitsford_weeks_philbrick_2015, title={UV resonance Raman signatures of phonon-allowed absorptions and phonon-driven bubble formation}, volume={9584}, booktitle={Ultrafast nonlinear imaging and spectroscopy iii}, author={Hallen, H. D. and Willitsford, A. and Weeks, R. and Philbrick, C. R.}, year={2015} }
 @article{brown_brown_edwards_liu_philbrick_2014, title={Measurement of atmospheric oxygen using long-path supercontinuum absorption spectroscopy}, volume={8}, ISSN={["1931-3195"]}, DOI={10.1117/1.jrs.8.083557}, abstractNote={Abstract The concentration of atmospheric oxygen is measured over a 540-m path using supercontinuum absorption spectroscopy. The absorption data compared favorably with MODTRAN™ 5 simulations of the spectra after adjusting for the differences of index of refraction of air and matching the instrument spectral resolution, as described by the effective slit width. Good agreement with the expected atmospheric oxygen concentration is obtained using a previously developed multiwavelength maximum likelihood estimation inversion algorithm. This study demonstrates the use of the SAS technique for measuring concentrations of chemical species with fine absorption structure on long-atmospheric paths.}, journal={JOURNAL OF APPLIED REMOTE SENSING}, author={Brown, David M. and Brown, Andrea M. and Edwards, Perry S. and Liu, Zhiwen and Philbrick, C. Russell}, year={2014}, month={Sep} }
 @inproceedings{hallen_neely_willitsford_chadwick_philbrick_2013, title={Coherence in UV resonance Raman spectroscopy of liquid benzene and toluene, but not ice}, volume={8845}, booktitle={Ultrafast imaging and spectroscopy}, author={Hallen, H. D. and Neely, R. R. and Willitsford, A. H. and Chadwick, C. T. and Philbrick, C. R.}, year={2013} }
 @article{li_schwemmer_prasad_hwang_lei_lee_prasad_philbrick_2013, title={Eye-safe compact Raman light detection and ranging temperature profiler}, volume={52}, ISSN={["2155-3165"]}, DOI={10.1364/ao.52.008540}, abstractNote={The vertical profile of atmospheric temperature is a principal state variable to study atmospheric stability. A lidar system, constructed using a 355 nm Nd:YAG laser transmitter, measures the temperature profile using the rotational Raman technique. In comparison with traditional Raman lidar, the major innovations are the use of a low peak power and high repetition rate laser to achieve eye-safe operation in a compact reliable instrument and the use of an angle tuning filter to select operating wavelengths. We demonstrate the capability of both nighttime and daytime measurements as a step toward a future stand-alone capability for routine measurements of important meteorological properties in the lower atmosphere.}, number={35}, journal={APPLIED OPTICS}, author={Li, Guangkun and Schwemmer, Geary and Prasad, Coorg and Hwang, I. H. and Lei, Jie and Lee, Sangwoo and Prasad, Narasimha S. and Philbrick, Russell}, year={2013}, month={Dec}, pages={8540–8548} }
 @inproceedings{hallen_long_hook_pangle_philbrick_2013, title={Multistatic lidar measurements of non-spherical aerosols}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Hallen, H. D. and Long, B. J. N. and Hook, D. A. and Pangle, G. E. and Philbrick, C. R.}, year={2013} }
 @inproceedings{pangle_hook_long_philbrick_hallen_2013, title={Optical extinction dependence on wavelength and size distribution of airborne dust}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Pangle, G. E. and Hook, D. A. and Long, B. J. N. and Philbrick, C. R. and Hallen, H. D.}, year={2013} }
 @article{willitsford_chadwick_hallen_kurtz_philbrick_2013, title={Resonance enhanced Raman scatter in liquid benzene at vapor-phase absorption peaks}, volume={21}, number={22}, journal={Optics Express}, author={Willitsford, A. and Chadwick, C. T. and Hallen, H. and Kurtz, S. and Philbrick, C. R.}, year={2013}, pages={26150–26161} }
 @inproceedings{hook_pangle_long_philbrick_hallen_2013, title={Understanding lidar returns from complex dust mixtures}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Hook, D. A. and Pangle, G. E. and Long, B. J. N. and Philbrick, C. R. and Hallen, H. D.}, year={2013} }
 @inproceedings{long_hook_pangle_hallen_philbrick_2013, title={Using a laser aureole to study aerosols}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Long, B. J. N. and Hook, D. A. and Pangle, G. E. and Hallen, H. D. and Philbrick, C. R.}, year={2013} }
 @article{zugger_kasting_williams_kane_philbrick_2011, title={Light scattering from exoplanet oceans and atmospheres (vol 723, pg 1168, 2010)}, volume={739}, DOI={10.1088/0004-637x/739/1/55}, abstractNote={Michael E. Zugger1,2, James F. Kasting2,3, Darren M. Williams2,4, Timothy J. Kane1,5, and C. Russell Philbrick6 1 Penn State University, Applied Research Laboratory, P.O. Box 30, State College, PA 16804, USA 2 Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802, USA 3 Department of Geosciences, Penn State University, 443 Deike Bldg., University Park, PA 16802, USA 4 School of Science, Penn State Erie, The Behrend College, 4205 College Drive, Erie, PA 16563-0203, USA 5 Department of Electrical Engineering, Penn State University, Electrical Engineering East, University Park, PA 16802, USA 6 Physics Department, North Carolina State University, 432 Riddick Hall, Raleigh, NC 27695–8202, USA Received 2011 May 17; published 2011 September 6}, number={1}, journal={Astrophysical Journal}, author={Zugger, M. E. and Kasting, J. F. and Williams, D. M. and Kane, T. J. and Philbrick, C. R.}, year={2011} }
 @article{zugger_kasting_williams_kane_philbrick_2011, title={SEARCHING FOR WATER EARTHS IN THE NEAR-INFRARED}, volume={739}, ISSN={["0004-637X"]}, DOI={10.1088/0004-637x/739/1/12}, abstractNote={Over 500 extrasolar planets (exoplanets) have now been discovered, but only a handful are small enough that they might be rocky terrestrial planets like Venus, Earth, and Mars. Recently, it has been proposed that observations of variability in scattered light (both polarized and total flux) from such terrestrial-sized exoplanets could be used to determine if they possess large surface oceans, an important indicator of potential habitability. Observing such oceans at visible wavelengths would be difficult, however, in part because of obscuration by atmospheric scattering. Here, we investigate whether observations performed in the near-infrared (NIR), where Rayleigh scattering is reduced, could improve the detectability of exoplanet oceans. We model two wavebands of the NIR which are “window regions” for an Earth-like atmosphere: 1.55–1.75 μm and 2.1–2.3 μm. Our model confirms that obscuration in these bands from Rayleigh scattering is very low, but aerosols are generally the limiting factor throughout the wavelength range for Earth-like atmospheres. As a result, observations at NIR wavelengths are significantly better at detecting oceans than those at visible wavelengths only when aerosols are very thin by Earth standards. Clouds further dilute the ocean reflection signature. Hence, other techniques, e.g., time-resolved color photometry, may be more effective in the search for liquid water on exoplanet surfaces. Observing an exo-Earth at NIR wavelengths does open the possibility of detecting water vapor or other absorbers in the atmosphere, by comparing scattered light in window regions to that in absorption bands.}, number={1}, journal={ASTROPHYSICAL JOURNAL}, author={Zugger, M. E. and Kasting, J. F. and Williams, D. M. and Kane, T. J. and Philbrick, C. R.}, year={2011}, month={Sep} }
 @article{snyder_brown_philbrick_2011, title={Sensitivity of the Polarization Ratio Method to Aerosol Concentration}, volume={8037}, ISSN={["1996-756X"]}, DOI={10.1117/12.884206}, abstractNote={A multiwavelength, multistatic optical scattering instrument is being developed to characterize spherical aerosols. This instrument uses 405 nm (blue), 532 nm (green) and 655 nm (red) diode lasers and two CCD imagers to measure the angular distribution of light scattered from aerosols. The incident light is polarized parallel or perpendicular to the scattering plane; the scattered intensity is measured at backscatter angles ranging from 120° to 170° by CCD imagers. The phase function for each polarization is used to form the polarization ratio, which is used to characterize the aerosols. This method has proven to be a reliable way to characterize spherical aerosols by matching the measured polarization ratio with the polarization ratio calculated by the Mie scattering equations. This method is used to determine the number density, size distribution, and index of refraction of the aerosols. The sensitivity of the polarization ratio to particle concentration is explored using a narrow distribution of one micron polystyrene beads in a chamber. The aerosol concentration is found via an inversion technique that is based on Mie calculations. This study provides the basis for transitioning this instrument to measure multiple particle size ranges and concentrations for common aerosols in an outdoor environment.}, journal={LASER RADAR TECHNOLOGY AND APPLICATIONS XVI}, author={Snyder, Michelle G. and Brown, Andrea M. and Philbrick, C. Russell}, year={2011} }
 @article{zugger_kasting_williams_kane_philbrick_2010, title={LIGHT SCATTERING FROM EXOPLANET OCEANS AND ATMOSPHERES}, volume={723}, ISSN={["0004-637X"]}, DOI={10.1088/0004-637x/723/2/1168}, abstractNote={Orbital variation in reflected starlight from exoplanets could eventually be used to detect surface oceans. Exoplanets with rough surfaces, or dominated by atmospheric Rayleigh scattering, should reach peak brightness in full phase, orbital longitude (OL) = 180°, whereas ocean planets with transparent atmospheres should reach peak brightness in crescent phase near OL = 30°. Application of Fresnel theory to a planet with no atmosphere covered by a calm ocean predicts a peak polarization fraction of 1 at OL = 74°; however, our model shows that clouds, wind-driven waves, aerosols, absorption, and Rayleigh scattering in the atmosphere and within the water column dilute the polarization fraction and shift the peak to other OLs. Observing at longer wavelengths reduces the obfuscation of the water polarization signature by Rayleigh scattering but does not mitigate the other effects. Planets with thick Rayleigh scattering atmospheres reach peak polarization near OL = 90°, but clouds and Lambertian surface scattering dilute and shift this peak to smaller OL. A shifted Rayleigh peak might be mistaken for a water signature unless data from multiple wavelength bands are available. Our calculations suggest that polarization alone may not positively identify the presence of an ocean under an Earth-like atmosphere; however, polarization adds another dimension which can be used, in combination with unpolarized orbital light curves and contrast ratios, to detect extrasolar oceans, atmospheric water aerosols, and water clouds. Additionally, the presence and direction of the polarization vector could be used to determine planet association with the star, and constrain orbit inclination.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Zugger, M. E. and Kasting, J. F. and Williams, D. M. and Kane, T. J. and Philbrick, C. R.}, year={2010}, month={Nov}, pages={1168–1179} }
 @inproceedings{philbrick_hallen_wyant_wright_snyder_2010, title={Optical remote sensing techniques characterize the properties of atmospheric aerosols}, volume={7684}, booktitle={Laser radar technology and applications xv}, author={Philbrick, R. and Hallen, H. and Wyant, A. and Wright, T. and Snyder, M.}, year={2010} }