The Q branch of the fundamental Raman band of the ordered phase of solid hydrogen and deuterium

The Raman transition ν = 0 → ν = 1, J → J has been studied in the ordered phase of solid o-H 2 containing ~5% p-H 2 , and of solid p-D 2 containing ~5% o-D 2 . Two new features of low intensity appear in the Q branch when the change from the disordered to the ordered structure occurs. One of the new features is sharp and is due to a vibrational excitation which is localized because, when the concentration of impurity molecules is low, the ordering of the molecules is distorted only locally about the impurity sites. The second new feature is broad and is due to simultaneous vibron–libron excitations. The frequency of the intense Q 1 (1) feature decreases by ~0.5 cm −1 on ordering due to an increase in the quadrupolar intermolecular interaction in the ordered phase; the Q 1 (0) feature is unaffected by the ordering.