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

High resolution threshold photoelectron spectroscopy, in conjunction w ith synchrotron radiation has been employed to investigate single and double photoionization of argon in the 32-51 eV photon energy range. W e 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 sect ions for satellite states from threshold to 150 meV. The excitation fu nctions of these electro-correlated processes generally show a strong threshold peak, which we attribute to dynamic effects within the excit ation complex, as well as other peaks due to the nearby neutral resona nces. In addition, the apparent asymmetry of the Ar2+ 1D threshold cus p is discussed in terms of a possible pressure effect.