Theory of theHe3Impurity "Gas" in SolidHe4

The nuclear-magnetic-resonance properties of dilute ${\mathrm{He}}^3$ impurities in solid ${\mathrm{He}}^4$ are analyzed on the basis of "gaslike" motions using a model Hamiltonian whose only parameters are the nearest-neighbor exchange matrix elements $J_{34}$ and $J_{33}$. It is shown that ${\mathrm{He}}_2^3$ "molecular" bound states exist in this model. The value of $J_{34}$ required to fit the experiment is not so "anomalously small" as previously reported.