Production and thermal annealing of neutrino-recoil-induced Frenkel pairs in copper

${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ atoms which originate from ${}_{}{}^{111}{}_{}{}^{}\mathrm{Sn}$ decays via electron capture start at the energy of 29 eV from substitutional lattice sites in otherwise undamaged copper and produce isolated single Frenkel pairs at 4.2 K. The observation of γγ perturbed angular correlations (PAC’s) following the decay of ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ to ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ yields the signal of the copper monovacancy of ${\nu }_Q$=$e^2$Qq/h=117 MHz (η=0). The thermal annealing behavior of the Frenkel pairs is studied by PAC in an isochronal (10-min) annealing program between 4.2 and 300 K. Two distinct annealing steps are observed: Between 35 and 48 K about 60% and between 250 and 293 K the remaining 40% of the monovacancies vanish. The first step is due to the recombination of vacancies with their own interstitial (correlated recombination), while the second one is caused by detrapping and free vacancy migration. Details of the process of Frenkel-pair production and consequences for defect models are discussed.