Abstract

Electrons can be bound at a surface by the Coulomb attraction to their image charge. The resulting image potential states form a hydrogenic series converging toward the vacuum level for zero parallel momentum k. Since their first experimental observation at the metal surface^1-4 they have been measursd with various experimental techniques. Here we report on the first measurement applying a pure optical method. It takes advantage of the enhancement of second harmonic generation (SHG) at the surface induced by a resonant transition.

© 1986 Optical Society of America