Location of Inert Gas Atoms in KCl, CaF2, and UO2 Crystals by H+ and He2+ ``Channeling'' Studies

Abstract

The α-particle emission rate of 222Rn, embedded in single crystals of KCl, CaF2, and UO2 at a concentration of 10−4−10−3 at. %, exhibits no detectable anisotropy—thereby proving that the radon atoms do not occupy single lattice vacancies and also, in the case of the fluorite structures, CaF2 and UO2, that they do not occupy the big interstitial holes either. The α-emission rate of the short-lived daughter isotopes (218Po and 214Po) also exhibits no anisotropy in the KCl, and CaF2 experiments. In UO2, however, the polonium α-peaks are attenuated markedly within 0.8°±0.2° of the 〈100〉 direction, indicating that the Po atoms are located along the 〈100〉 lattice row. Similarly, wide-angle Rutherford scattering of protons has been used to show that Xe, embedded in KCl at a concentration of 0.2 at. %, does not occupy single lattice vacancies.