Yields of bulk plasmons excited by slow Neq+ ions interacting with an Al surface

Low-energy electron emission spectra measured during the interaction of 4.5 keV Neq+ ions with an Al surface for incident charge states q = 1 to 6 wer e studied and signatures for bulk plasmons at 11 eV were analyzed. Recent m easurements of the bulk plasmon yield for 4.5 keV Ne5+ impinging on Al show a dependence on the observation angle. The yield of the bulk plasmons was examined with respect to the projectile charge for a fixed observation angl e. Two processes are considered to be responsible for the production of bul k plasmons: excitation by plasmon-assisted electron capture and by fast ele ctrons. (C) 2000 Elsevier Science B.V. All rights reserved.