Electron excitation in the interaction of slow ions and electrons with metals and monolayer graphite on Ni(111) surfaces

We report on the experimental energy distributions of electrons emitted in the interaction of slow ions and electrons with aluminium and with monolayer graphite deposited on a Ni(111) surface. Measurements on the Al surface clarify the role of plasmon decay in secondary electron emission. In contrast with theoretical calculations, our experiments indicate that the electron collision cascade inside the solid produced by electrons excited by plasmon decay does not contribute significantly to electron emission. The energy distribution of electrons emitted in the interaction of He+ ions with monolayer graphite reveal a high-energy feature that can be attributed to the autoionization decay of excitonic states populated by electron promotion in close He–C encounters.