MULTIPLE PHOTOIONIZATION OF K AND CA ATOMS IN THE L-SHELL IONIZATION REGION

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.