Vibrational and rotational frequency shifts of dilute H2, D2, and HD impurities in solid Ar, Kr, and Xe under pressure

The frequency shifts from gas phase values of the vibrational and rotational states of H2, D2, and HD molecules matrix isolated in solid Ar, Kr, and Xe are calculated at zero temperature and at pressures 0≤P≤570 kbar. Also calculated are the impurity local mode frequencies versus pressure. It is found that the pure vibrational and rotational-vibrational transitions are strongly red shifted in the solid P = 0, compared to the gas phase values. This shift is greatest for Xe and smallest for Ar host lattices. The agreement with Raman scattering experimental data is good. The pure rotational transitions also show a small red shift at P = 0 in the solid, and are in generally good agreement with the measurements of Jodl and Bier [I] but not with those of Prochaska and Andrews [2] who, except for D2 (Ar) measure small blue shifts. With increasing pressure all transitions are strongly blue shifted with respect to P = 0 solid frequencies, except at relatively low pressures where most of the modes of H2, D2. and HD in Xe and Kr are initially red shifted. The calculated local mode frequencies of the impurity molecules in the solid at P = 0 are in good agreement with experiment [2], and are strongly blue shifted with increasing pressure.