(He3)2Molecules in SolidHe4

The general features of $T_1\left(\omega \right)$ data on dilute ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in solid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are explained in terms of coupled rotation-translation motions of ${\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)}_2$ molecules bound together by the elastic ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ interaction. As the concentration of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is lowered the molecular motions become two-dimensional and give rise to the anomalous structure observed in the $T_1\left(\omega \right)$ spectrum.