Rotational excitations in concentrated solid Kr-CH4 solutions.   Calorimetric studies
  The heat capacity of solid Kr-CH4 solutions with 30 and 60 mol.% CH4 has been studied at 0.8-20 K. The contribution of the rotational subsystem Crot to the heat capacity of the solutions is separated. The results obtained in this study and Ref. [4] were used to estimate the difference between the lowest-level energies of the nuclear spin A and T modifications of CH4 and to find the characteristic conversion times for the solutions with 5-60 mol.% CH4 at low temperatures. 
M.I. Bagatskii, V.G. Manzhelii, I.Ya. Minchina, D.A. Mashchenko, I.A.   Gospodarev