Matrix isolated alkali halide monomers and clusters

Abstract

The far infrared absorption spectra of sodium and cesium halide monomers and clusters isolated in solid argon are reported. For low concentrations of alkali halide vapor in argon, four absorption lines were usually seen. The strongest and highest frequency line could be assigned to the monomer. The three remaining lines were due to planar rhombic dimers. For higher concentrations of alkali halide vapor, new absorption lines appeared which seem to be due to trimer and tetramer formation. The equilibrium configurations of alkali halide molecules containing from two to eight atoms were calculated by minimizing the total energy. Both rigid and polarizable ion models were used to describe the two particle interaction. The second derivative of the total energy with respect to the atomic displacements was then calculated and the resulting dynamical matrix diagonalized to give the infrared absorption spectrum.