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

Zero-degree electron spectra were measured with high resolution for 64 MeV Sq+ (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 S12+ + He collision, in addition to a series of autoionization electrons produced by the Coster-Kronig transition 1s(2)2p(P-2(3/2))9l-1s(2)2s epsilon l'. The charge state dependence of electron spectra for 64 MeV S-11+,S-12+,S-13+ + He and S-6+,S-12+,S-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 S13+ 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 S13+ ions and a He target at this collision energy. It is supposed that the electron spectra for S11+ shows a series of autoionizing Coster-Kronig transitions of 1s(2)2p(2)7l-1s(2)2s2p epsilon l', 1s(2)2p(2)9l-1s(2)2s2p epsilon l' and 1s(2)2s2p9l-1s(2)2s(2) epsilon l' for S11+ ions, which are energetically possible.