Single Frenkel-Pair Production by Neutrino Recoil

The decay of ${}_{}{}^{111}{}_{}{}^{}\mathrm{Sn}$ to ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ via electron capture is employed for the first observation of a solid-state effect caused by nuclear recoil due to neutrino emission. The monoenergetic ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ recoil atoms of 29 eV start from substitutional lattice sites in copper and produce isolated, single Frenkel pairs. The effect is traced by observation of $\gamma \gamma$ perturbed angular correlations following the decay ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ to ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$.