Near-Threshold K-Shell Photoionization Of Argon

The K-shell photoionization cross section of argon near the threshold has been obtained with the multiconfiguration Hartree-Fock method for continuum wave functions. The electron correlation and the core-relaxation effects that are very important in this process have been taken into account in the calculation very accurately in the ab initio manner through the configuration-interaction procedure. The present results are compared with the experimental measurements and are found to be in excellent agreement. The two-electron resonances that have been observed immediately above the ionization threshold have been identified and assignments have been made to these based on accurate calculations