Optical Emission from Irradiated Foils. I

The present work is concerned with the emission of optical radiation from foils irradiated with charged particles. A generalization of the Ginsburg-Frank treatment is presented in which the wave properties of normally incident charged particles are accounted for in the Born approximation. The foil is assumed to be of finite thickness and to possess a dielectric constant of the form $\ensuremath{\epsilon}(\ensuremath{\omega})={\ensuremath{\epsilon}}_{1}(\ensuremath{\omega})+i{\ensuremath{\epsilon}}_{2}(\ensuremath{\omega})$. Detailed prediction of the energy and angle distribution of emitted photons is made. The present result is shown to reduce to that obtained by Ferrell if $\ensuremath{\epsilon}(\ensuremath{\omega})$ appropriate to a free electron gas is assumed and if one takes $\frac{{v}_{i}}{c}\ensuremath{\ll}1$, where ${v}_{i}$ is the speed of the incident particle. Numerical results have been obtained for foils of Ag and Al.