Diffusion in Inert‐Gas bombarded KCl, KBr, and KI

A study of inert‐gas diffusion, mainly involving Kr and Xe, in ion‐bombarded KCl, KBr, and KI has been made using bombardment energies up to 85 keV and doses up to 50 μA min/cm2. Two types of release behavior were observed, both of which were shown to be compatible with diffusion kinetics, at least to first approximation. Low doses led to release with a fairly well‐defined ΔH of 33.5, 30.5, and 28.5 kcal/mol for KCl, KBr, and KI respectively, while high doses led to release with a somewhat variable ΔH having mean values of 44, 39, and 33.5 kcal/mol for KCl, KBr, and KI respectively. It is proposed that the low‐dose release involves gas motion without an implied gas—gas or gas—damage interaction, the gas perhaps occupying the small, stable vacancy clusters recently discussed by one of the authors (Hj. M.). The high‐dose release seems, by contrast, to be affected by transient gas—gas or gas—damage interactions, and is probably identical with the process found in homogeneous‐labelling work between about 250 °C and the “knee” temperature. A third type of release, found in homogeneous‐labelling work above the “knee”; temperature, has no parallel in ion‐bombardment work. It is here tentatively attributed to the motion of small, gas‐filled bubbles, and its ΔH of 7 to 14 kcal/mol is proposed to be related to that for surface diffusion of the host crystal.