The rotation of methane molecules in the crystalline state above and below the temperature of the phase α-β transition

Abstract

The work is devoted to the study of rotational features of methane molecules in the methane solid state in different temperature ranges. We formulated earlier, the concept of the description of collective rotational motion of the CH4 molecules with the use of a topon quasi-particle. This approach received a new experimental confirmation in papers by Yu. A. Dmitriev and N. P. Benetis on studying by electron paramagnetic resonance (EPR) quantum mechanical rotation of CH3 radicals matrix isolated in solid methane and in a work by P. Pyykko using nuclear magnetic resonance (NMR) technique to test rotation of host molecules in methane at temperatures of orientational ordering (below the α−β transition). Comparison with the behavior of the CH3 radical in other orientation-ordered matrices, CO2, N2, CO, N2O suggests that the observed change in the barrier at such low temperatures is associated with the reorientation of the methane matrix molecules, which, provided that their orientation ordering is preserved, is possible only as a result of collective tunnel rotation.