Ejected-electron spectra from Rydberg states in high-energy collisions of O3+ ions with He

High-resolution Coster-Kronig (C-K) electron emission spectra in collisions of 32 MeV O3+ ions with a He gas target have been investigated using zero-degree electron spectroscopy. Zero-degree electron spectrum for the O3+ projectiles exhibits a trident-like structure around the cusp peak, consisting of three clear peaks. The sharp peaks directly on either side of the cusp corresponded to autoionization lines from highly excited O3+ ions produced in the collision with a He gas target, which are confirmed to be due to the configuration 1s22s2p(3P)5s, where the C-K ejection energy is 0.014 eV. The C-K transitions in higher energy region are found to originate in 1s22s2p(3P)nl-1s22s2 εl' (n = 5-11). For n = 5-7, a clear angular momentum distribution is observed, where the maximum intensity is attributed to the relatively high angular momentum l = 2 or 3