Irradiation-Induced Expansion of Alkali Halide Crystals at Room Temperature

The reflected x-ray intensities in the vicinity of a Bragg maximum are given for irradiated and unirradiated NaCl single crystals and the fractional increase in lattice parameter, ( DELTA d/d), is calculated from these data. The fractional F-center density and one-third the fractional volume expansion, as determined from photoelastic data, is plotted versus ( DELTA d/d) for several samples of LiF. The data indicate a substantial increase in the lattice parameter of alkali halide single crystals following x irradiation at room temperature. This suggests that interstitials are generatedand/or that there is considerable relaxation in the vicinity of the vacancies. (H.D.R.)