Zur Diffusion aus einem verdampfenden Probekörper (Edelgasdiffusion in Festkörpern 18)

Summary

A body is considered with a uniform distribution of dissolved gas at the time t = 0. For t > 0, diffusion of the gas and simultaneous evaporation of the body is assumed. For sufficiently small evaporation, the corresponding diffusion problem with time variable boundary condition can be solved by successive approximation. This is done in first order for a sphere. For larger evaporation, approximation formulas for the resulting gas release in small times (small diffusion depth) are obtained in an elementary way. The approximation equations are valid for more general body formes and in agreement with the above result. The calculation of the diffusion coefficient from the release curve is discussed.