A tentative explanation is given of experiments concerning the dependence of the brightness of a luminescent material on the voltage of electron bombardment. A model is assumed in which surface effects prevail over luminescence in using radiation energy. The possibility of a quantitative theoretical treatment is largely due to symmetry properties in the diffusion of scattered electrons in a solid body.

• Received 31 May 1940

DOI:https://doi.org/10.1103/PhysRev.58.544