Low-energy Rydberg electron spectra from 64 MeV S q+ + He and C-foil collisions using zero-degree electron spectroscopy

Abstract

Zero-degree electron spectra were measured with high resolution for 64 MeV S q+ ( q = 6, 11 to 13) ions on a He and C-foil target. Several peaks are observed in the electron energy range up to 2.5 eV for the 64 MeV S 12+ + He collision, in addition to a series of autoionization electrons produced by the Coster-Kronig transition 1 s 22p( 2P 3 2 )9l−1 s 22s ϵl′ . The charge state dependence of electron spectra for 64 MeV S 11+.12+.13+ + He and S 6+.12+.13+ + C were measured to identify the origin of the low energy electrons. No characteristic line is observed in the electron energy spectra following the 64 MeV S 13+ beam excitation with He. This indicates that the electron excitation and capture process that could produce the Li- and Be-like initial configurations resulting in autoionizing Coster-Kronig transitions does not occur during a collision between 64 MeV S 13+ ions and a He target at this collision energy. It is supposed that the electron spectra for S 11+ shows a series of autoionizing Coster-Kronig transitions of 1s 22p 27 l−1s 22s2p ϵl′, 1s 22p 29 l−1s 22s2p ϵl′ and 1s 22s2p9 l−1s 22s 2 ϵl′ for S 11+ ions, which are energetically possible.