Multiple photoionization of K and Ca atoms in the L-shell ionization region

Abstract

The charge state distribution of photoions from K and Ca targets has been measured in the L-shell ionization region (270-400 eV for K, 330-500 eV for Ca) using a time-of-flight technique coupled with synchrotron radiation as a light source. In both the K and the Ca targets, doubly and triply charged ions are the prominent products, and outstanding doublet peaks due to the 2p-3d resonance excitation are observed in the yield spectra. The doubly charged K²⁺ ion predominates over the K³⁺ ion throughout the present energy range. On the other hand, the Ca²⁺ ion is the most intense species below the 2p ionization threshold and the Ca³⁺ ions dominate over Ca²⁺ ions above the threshold. These features of the photoion can be understood mainly by successive Auger decays from the 2p-shell vacancy states. The yield of higher charged ions indicates some contribution of shake processes.