Ar 2p shake-up structures studied by threshold electron spectroscopy

Abstract

Threshold electrons and photoions have been measured in the vicinity of the Ar 2p-13p-1 nl shake-up region using a coincidence technique. The threshold electron spectrum exhibits conjugate shake-up structures due to dipole transitions on the lower energy side of normal shake-up structures due to monopole transitions. The shake-up structures are identified with the aid of multiconfigurational Dirac-Fock energy calculations. The Ar3+ photoions in coincidence with threshold electrons are observed with significant intensities at the shake-up states. It is proposed that the Ar3+ formation is promoted by two-step decays besides Auger shake-off decays from the shake-up states.