Excitation of triply excited Be+ (2lnl ' n ' l '') states in 300 and 500 keV-Be++CH4 collisions
Bruch, R., Merabet, H., & Chung, K. T. (2003, May). NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, Vol. 205, pp. 488–493.
Abstract We have studied high resolution beryllium Auger electron spectra in the 120–160 eV projectile electron energy range following intermediate energies (1.2 and 1.5 a.u. impact velocities) in Be + + CH 4 ion–molecule single collisions [Comments At. Mol. Phys. D 14 (1984) 117]. The major focus of this study is the double K-shell excitation of the Be + projectile forming triply excited BeII*** states (hollow atoms) and BeIII** K shell ionization plus excitation of BeII doubly excited states with two inner shell vacancies. In such intermediate velocity ion-molecular collisions, the CH 4 target plays an important role in the enhancement of the population of BeII*** triply excited states when compared to a more tightly bound He (1s 2 ) 1 S ground state target. Due to the pioneering theoretical work of Gou and Chung [Phys. Rev. A 29 (1996) 6103] most line structures can now be unambiguously identified. The main triply excited states are associated with the 2s 2 2p, 2s2p 2 and 2p 3 and 2 l 2 l ′ n ′ l ″ ( n =3 and 4) configurations decaying to different final BeIII (1snl) ionic states. The line identification method used here is based on Auger energy levels, decay channels and branching ratios.