The crystalline site symmetry and its effect on the vibrational spectra of a weakly hindered molecule. V. Crystallization effects in NH4B(C6H5)4

Abstract

Changes in the vibrational spectra for molecules that nearly freely rotate or perform rotational tunneling at low temperatures are explained through the systematic study of the combined symmetry of the molecule, the site, and the molecule’s nuclear spins. The changes observed for different crystallizations in the low temperature vibrational spectra of the NH+4 ion dilute in KTPB and in NH4B(C6D5)4, the NH3D+ ion in ATPB and NH4ClO4, and of solid CH4 II are examined and explained as arising from slight perturbations of the crystalline site symmetry.