Raman spectra of matrix isolated hydrogen and deuterium chloride: Monomers and dimers.

Abstract

Matrix isolated HCl and DCl Raman spectra have been obtained and analyzed for monomers and dimers. The monomer spectrum contains only the Q pure vibration branch and a S 0 vibration-rotation line which positions are compatible with the infrared absorption results. Two lines have been assigned to the dimers on the basis of their intensity behaviour, i.e., a comparison between calculated and measured intensities relative to the monomer Q branch for various concentrations, experimental observations being made under the proper conditions to obtain randomly distributed solute molecules. A calculation based on intermolecular forces taking into account dipole-dipole, dipole-quadrupole and quadrupole-quadrupole interactions shows that the observed frequencies are best reproduced with the two molecules of the dimer at a nearly orthogonal position. This indicates that the quadrupole-quadrupole forces are the leading interaction in such a system.