Single-photon multiple ionization of argon in theK-edge region

Abstract
The individual charge state and total ion yields resulting from the photoionization of argon gas have been measured as a function of photon energy through the K edge using synchrotron radiation and time-of-flight spectroscopy. We have formulated a model for the mean ion charge q¯(hν) observed at nominal photon energy hν, and have determined the mean ion charge q¯ resulting from the decay of the atom following [1s]4p, [1s]5p, and [1sp photoabsorption. We have also characterized the energy-dependent photoelectron recapture probability due to postcollision interaction. In contrast with the recent analysis by Doppelfeld et al. [J. Phys. B 26, 445 (1993)], we find that the gradual increase in q¯(hν) that begins approximately 20 eV below the argon K edge can be attributed to lifetime energy broadening of the K-hole state and the finite energy width of the x-ray source.