The effect of electron bombardment on evaporated films of sodium aluminium fluoride

Dramatic changes in the secondary emission coefficient, delta, of sodium aluminium fluoride films occur upon electron bombardment. Initially delta decreases rapidly due to loss of fluorine atoms, leaving a surface rich in metallic sodium. The kinetics of fluorine desorption indicate that fluorine diffusion from the bulk to the surface occurs together with the loss from the surface. After the initial rapid decrease delta begins to rise again. This is probably a result of oxidation of metallic sodium in the surface layer by gases in the vacuum ambient. (Auth.)