Knowledge Bank

“Two low-temperature infrared cells, on for the solid phase and one for the liquid phase, have been used for the study of molecular motions of hydrogen halides in condensed rare gases. Both cells are designed for controlled temperature cycling and temperature regulation during the long experiments necessary for the detailed determination o data. The solid-phase cell operates in the rang $4.2\circ K-40\circ K$, while the liquid-phase cell operates above $77\circ K$. Vibration-(quasi) rotation spectra of the hydrogen halides in both liquid and solid rare gases will be discussed. The solid-phase spectra show P-and R-branches but at most a very weak Q-branch. These spectra are analyzed with respect to the site symmetry of the rare-gas crystal. Spectral shifts for vibrations and barriers for molecular rotation in crystalline argon, krypton, and xenon have been obtained. In the liquid phase the spectra show strong Q-branches along with P-and R-branches. An investigation of the absolute intensities of the hydrogen halides in liquid rare gases is in progress. Preliminary results for the 1-0 band of HCl in liquid xenon indicate an intensity enhancement of roughly a factor four over that of the free molecule.”