Determination of surface-plasmon dispersion relation by ricochet photoemission.

Abstract

Photoelectrons emitted along a metal surface from atoms located at a small distance outside that surface have a high probability to ricochet with the excitation of a surface plasmon if the angle of emergence $\ensuremath{\alpha}$ is less than a critical angle ${\ensuremath{\alpha}}_{M}$. The line shape of the surface-plasmon satellite ${I}_{1}({\ensuremath{\varepsilon}}_{k},\ensuremath{\alpha})$ peaks strongly at $\ensuremath{\alpha}=0$ and presents another peak at $\ensuremath{\alpha}={\ensuremath{\alpha}}_{M}$. Experiments are suggested to locate the second peak and thereby determine ${\ensuremath{\alpha}}_{M}({\ensuremath{\varepsilon}}_{k})$, a function which should yield direct information on the form and the parameters of the surface-plasmon dispersion relation.