Self-diffusion of chloride ions in rubidium chloride and exchange reaction between chlorine gas and the crystallites

Abstract

The isotopic exchange reaction between rubidium chloride and chlorine gas was studied in a carefully evacuated vacuum system, and also the self-diffusion of ³⁶Cl in powdery rubidium chloride below 400°C. The exchange reaction proceeded layer by layer with activation energies of 6 and 17, 22 and 28 kcal/mole for the more active and the less active domain of the first, the second and the third layer, respectively. The last value was close to the activation energy of self-diffusion. Therefore, the effect of the surface penetrates only up to the second layer, and this result is in harmony with the Benson theory on surface distortion. The self-diffusion is described by a model of a semi-infinite homogeneous medium, in spite of the probable existence of many dislocation lines.