Thermal expansion of solid solutions Kr-CH4 at temperatures of liquid helium

摘要

A negative contribution of the CH4 impurity to the thermal expansion of thesolution has been revealed in dilatometric studies of solid Kr+0.76% CH4,Kr+5.25% CH4 and Kr+10.5% CH4 solutions at 1-23 K. It is shown that thenegative contribution results from changes in the occupancy of the ground stateof the A-modifications of isolated CH4 molecules. Assuming that the CH4impurity singles and clusters contribute to the thermal expansionindependently, we can estimate their contributions. The contribution of thesingles to the thermal expansion of the solid solution is negative. Theenergies of the first excitational rotational states were determined forsingles and two-body and three-body clusters of CH4 molecules.