Ordering of cross sections for electron capture from He-like targets by fast projectiles

The continuum-distorted-wave (CDW) method is used to determine total electron-capture cross sections Q=Σ/sub n/lsigma[nl] for proton and α-particle projectiles incident on Li+ in energy ranges of 100< or =E< or =3000 keV and 100< or =E< or =10 000 keV, respectively. A configuration-interaction (CI) wave function is used to describe the Li+ electrons; for comparison, capture cross sections for H- and He are examined. For each system the percentage change in Q, Δ (HF→CI), is given for progression from a Hartree-Fock (HF) to a CI description of the target electrons. The main emphasis in this work is devoted to a rationalization of the trends observed in the ordering of Q for these three targets. This was achieved by an analysis of the CDW expression for an individual capture cross section sigma[nl, n'l'], where nl and n'l' are the states of the ''active'' (captured) and ''passive'' electrons, respectively