SATELLITE AND RESONANCE STATES IN THE NEAR-THRESHOLD PHOTOIONIZATION OF ARGON

High resolution threshold photoelectron spectroscopy, in conjunction with synchrotron radiation has been employed to investigate single and double photoionization of argon in the 32-51 eV photon energy range. We have been able to distinguish between satellite and resonance states observed in our spectrum and thereby correct previous misassignments. Furthermore, we have developed a method to extract partial cross sections for satellite states from threshold to 150 meV. The excitation functions of these electro-correlated processes generally show a strong threshold peak, which we attribute to dynamic effects within the excitation complex, as well as other peaks due to the nearby neutral resonances. In addition, the apparent asymmetry of the Ar2+ 1D threshold cusp is discussed in terms of a possible pressure effect.