Valence electron momentum distributions of the hydrogen halides. II. Comparison of EMS measurements and calculations using near Hartree-Fock limit and configuration interaction wavefunctions for hydrogen chloride

Abstract

The valence orbital electron momentum profiles of hydrogen chloride have been obtained by symmetric non-coplanar electron momentum spectroscopy at an impact energy of 1200 eV. The measurements are significantly different from earlier reported EMS profiles (J. Electron Spectry. Relat. Phenom. 21 (1980) 71) for the (5σ) −1 and (4σ) −1 processes. The measured momentum profiles are compared with calculated cross-sections using a range of wavefunctions from minimal basis to essentially Hartree-Fock limit in quality. The experimental momentum resolution is incorporated into the calculated momentum profiles using the recently developed GW-PG procedure (Chem. Phys. 159 (1992) 347). The effects of correlation and relaxation on the calculated momentum profiles are investigated by MRSD-CI calculations of the full ion-neutral overlap distributions. For all three valence profiles, the inclusion of many-body effects is found to provide little further improvement in the already quite good fit of theory to experimen at the near Hartree-Fock limit level, as has been found previously for other third row hydrides. The effects of final state correlation on the valence binding energy spectrum are investigated using MRSD-CI calculations and the results are compared with other calculations and with experiment.