DOUBLE-ELECTRON CAPTURE IN LOW-ENERGY FE17++HE COLLISIONS

Double electron transfer processes for the system Fe17+ + He have been studied utilizing high-resolution Auger electron spectroscopy. A thor ough analysis of the experimental conditions (single collision conditi on and metastable fraction content at the incident ion beam and their influence) has been performed, leading to the following conclusions. T he double capture leads to the preferential population of 2p(5)5l8l' c onfigurations sharing their decay between Auger processes and radiativ e cascade transitions. The observed sodiumlike ''quartet'' and ''doubl et'' states result from cascade contributions from higher-lying levels . Tentative mechanisms for the production of the quartet states are su ggested using a spin-flip model.