Heat capacity of dilute solid solutions of diatomic molecules in the matrix of inert gases

Abstract

A consistent theory is developed to describe temperature and concentration dependences of the excess impurity heat capacity of solid solutions of $^{14}\mathrm{N}_{2}$, $^{15}\mathrm{N}_{2}$, and ${\mathrm{O}}_{2}$ molecules in the matrix of inert gases Ar and Kr. It is shown that internal strain fields together with rotational degrees of freedom of the dissolving molecule contribute significantly to the thermodynamics of solutions already at concentrations about 0.1%. A comparison between obtained results and experimental data showed that the proposed theory is in good agreement with experiment up to the impurity concentrations of 1%.