Relativistic configuration interaction study of the ClF molecule and its emission spectra from 0+ ion-pair states

Abstract

An ab initio configuration interaction (CI) study including spin–orbit coupling is carried out for numerous valence and ion-pair states of the ClF molecule by employing relativistic effective core potentials. The computed spectroscopic constants are in good agreement with available experimental data for both valence and ion-pair states. The present calculations accurately reproduce the measured spin–orbit splittings for the first Π3 multiplet and confirm the recent corrected spectroscopic parameters for the A 3Π1 state [V. A. Alekseev, D. W. Setser, and J. Tellinghuisen, J. Mol. Spectrosc. 195, 162 (1999)]. The electronic structure of the six lowest ion-pair states of ClF which correlate to the Cl+(3P)+F−(1S) limit is analyzed in detail. It is shown that strong homogeneous perturbations of the E0+ and f0+, β1, and G1 states are mainly caused by an avoided crossing of the 3 3Π and 2 3 Σ− parent Λ–S states. The electric-dipole transition moments have also been calculated for transitions from the E and f ion-pair states to the lower-lying 0+ valence states. Emission spectra for the bound–bound and bound–free transitions have been computed on this basis and found to be in good agreement with the measured spectra. A similar analysis for the ion-pair D′2, β1, and G1 states will be presented in the subsequent study.