Angular momentum distributions of Rydberg state electrons of Be-like sulfur produced through foil penetration

Spectra for Coster–Kronig (C–K) transition 1s 2 2pð 2 P3=2Þ9l ! 1s 2 2sð 2 S1=2Þel 0 of Be-like S 12þ ions produced following penetration of 2.5 MeV/u S qþ ions (q ¼ 7, 10, 12, 13) through C-foil targets of various thickness (1–6.9 lg/cm 2 ) have been probed using zero-degree electron spectroscopy. It has been found that in collisions for S qþ (q ¼ 7, 10) ion incidence, in which the C–K electrons originate from the projectile bound electrons, a fraction of the angular momentum l ¼ 1 of the Rydberg state decreases, and fractions of higher ðl P 2Þ angular momenta increase, while the total intensity of the C–K electrons grows, as target foil thickness increases. The electron spectra for S qþ (q ¼ 13) incident ions, in which the autoionizing Be-like state is preferably formed by electron capture from the target continuum upon or near the exiting surface, do not change in l-distribution or intensity. The shift to higher l comes from the multiple collisions of electron with the target, in traveling at the same speed under the strong Coulomb potential of the projectile. The observed dependence of the l-distribution and the intensity of the Rydberg state on projectile initial charge and target thickness indicates the importance of transport phenomena for both the S 13þ core and the projectile-entrained electrons inside solid. 2002 Elsevier Science B.V. All rights reserved.