Low-energy ion neutralization at surfaces: Resonant and Auger processes

N. P. WANG; GARCIA E.; R. MONREAL; F. FLORES; E. C. GOLDBERG; H. H. BRONGERMA; P. BAUER

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

AMER PHYSICAL SOC

Lugar: New York; Año: 2001 vol. 64 p. 129011 - 129019

1050-2947

The interaction of He1 with a typical metal surface ~Al or Pd! is described, analyzing in detail the differentmechanisms that contribute to the neutralization of the projectile when backscattered from the surface. Augerand resonant neutralization processes are considered and analyzed including a detailed quantum-mechanicaldescription of the He-metal interaction, for projectile energies between 100 eV and 3 keV. We show that thepromotion of the He-1s level, due to its interaction with the metal-atom-core orbitals, is the crucial mechanismmaking resonant processes operative. We find, however, that resonant processes are much more important forAl than for Pd. In Al, both Auger and resonant processes are equally important for neutralization of the ion,while for Pd we find that Auger is the dominant mechanism, making the He/Pd system the ideal case for whichHagstrum’s exponential law appears to be practically valid for all velocities. We also find qualitative agreementwith experimental data, which we consider a satisfactory result in view of the fact that our theory is acomplex ab initio calculation free of adjustable parameters.