ATOM-MOLECULE VAN-DER-WAALS COMPLEXES CONTAINING OPEN-SHELL ATOMS .2.THE BOUND-STATES OF CL-HCL

The methods needed to carry out calculations on the bound states of at om-molecule Van der Waals complexes containing atoms in P states are p resented. Both close-coupling and helicity decoupling (coupled states) formalisms are described. The anisotropy of the interaction potential and the atomic spin-orbit coupling are fully included. The formalism is also applicable to the scattering of molecules by P-state atoms. Th e methods are applied to the vibration-rotation energy levels of the C l-HCl Van der Waals complex. An intermolecular potential for Cl-HCl th at is valid at long range is constructed, based on knowledge of the Ar -HCl, Ar-Cl, and Ar-Ar potentials. There are important electrostatic c ontributions arising from the atomic quadrupole of the Cl atom. Bound- state calculations are performed, using both helicity decoupling and c lose-coupling calculations. The patterns of bending and stretching vib ronic levels and the rotational structure are investigated. The microw ave spectrum and the frequencies of the main bands in the far-infrared and mid-infrared spectrum are predicted.