Strong Increase of Tunneling Rate of Hydrogen in Indium in the Presence of Vacancies

The data on the influence of point defects on the rate of hydrogen tunneling in a crystal lattice of a solid have been obtained for the first time. It is established that vacancies in indium of no more than 0.1 at. % increase the coefficients of quantum diffusion of deuterium by a factor of 30. The vacancies were produced by irradiation of specimens with deuterons; the diffusion coefficients were determined in the temperature range from liquid nitrogen to 125 K using the accelerating technique of nuclear reactions; the type of defects affecting the tunneling rate was identified by the method of isochronous annealings. The results are discussed in the model of quantum diffusion proposed by Flynn and Stoneham for light interstitial atoms in metals. The strong accelerating impact of vacancies on the tunneling rate is traceable to a decrease in the distance between equilibrium positions for deuterium atoms in the crystal lattice.