Isotopic Impurity Tunneling in SolidHe4

Abstract

A study has been made of the motion of isotopic impurities in solid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. The tunneling frequency of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ atoms with neighboring ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atoms in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ lattice has been deduced from nuclear magnetic relaxation measurements. The volume variation of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ tunneling rate is much greater than that of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ tunneling rate (exchange).