Effects of heavy impurities on thermodynamic properties of solid hydrogen

The influence of a heavy substitutional impurity on the thermodynamics of the rotational sub-system of solid hydrogen is studied. A splitting of 3°K is found for the rotational level of the orthohydrogen molecule with the heavy impurity as the nearest neighbour on the assumption that the heavy isotopic impurity suppresses short-range dynamic correlations. The contribution of impurity-orthomolecule pairs to the thermodynamics of the rotational sub-system is also studied. The calculated values are in a fair agreement with experiment.