Infra-red cryogenic studies. Part 2.—Effect of matrix environment on hydrogen halide monomers

Abstract

A study has been made of the bands arising from monomeric species of HCl, HBr, and HI in low concentrations in a variety of matrices at 20 K. The presence of hindered rotation, already well established in noble gas matrices, is found also to occur in CH₄, CF₄ and SF₆ matrices. Rotation of the HX solute molecule is prevented in N₂, CO, CO₂, and C₂H₄ matrices, monomer doublet frequencies being attributed to multiple trapping sites. The formation of a specific complex is believed to occur in an thylene matrix. The observed matrix-induced frequency shifts of the hydrogen halides are compared with each other and with theoretical values calculated in terms of electrostatic, inductive, dispersive and repulsive interactions.