Population of the states in collisions of mixed‐state (1s21S,1s2s3S) B3+ and C4+ ion beams with He and H2 targets

Abstract

Auger KLn lines are observed in high‐resolution electron spectra obtained in collisions of mixed‐state (1s21S,1s2s3S) He‐like beams of 4 MeV B3+ with H2 and 6 MeV C4+ with He targets. Supporting atomic structure calculations show these lines to correspond to doubly excited states, which can be readily populated by electron transfer to the component of the mixed‐state beam. They thus provide indirect evidence for the existence of the corresponding KLn quartet states, similarly produced, even though their weak Auger decay does not allow for their direct observation in the electron spectra. These KLn quartet states mostly decay in a cascade chain of strong radiative E1 transitions, eventually terminating at the state, which is thus additionally enhanced. An upper limit on the state population due to cascades is obtained by assuming a statistical production of KLn quartet to doublet states followed by a 100% cascade feeding of the state. Our estimated upper limit is supported by our absolute cross section measurements and corresponding three‐electron atomic orbital close coupling calculations in progress. Results to date are presented and discussed.