# Theory of Desorption of Neutrals by Temporary Ionization of Physisorbed Species at Metal Surfaces

## Abstract

Electron or photon stimulated desorption (ESD or PSD, respectively) is a sensitive probe for studying atomic or molecular systems in interaction with solid surfaces /1,2/. Apart from fragment ions in some cases of physisorbed molecules, only neutral adsorbate species desorb from physisorbed layers /3–7/. This fact is understood in terms of a classical model, due to ANTONIEWICZ /8/ in which the desorption process is a sequence of three steps denoted by 1, 2, and 3 in both panels of Fig. 1. Total electronic energy of the adparticle - solid system depends on the adparticle’s distance from the solid surface and on the state of an electronic excitation the solid and the adsorbed particle are in. For physisorption the electrons in the solid and on the adparticle can be considered separately. Thus, the electronic diabatic configuration in which the solid and the adparticle are in their respective electronic ground states corresponds to the energy level V_{O} and V_{O}(z) is the surface potential for the physisorbed neutral. In a configuration corresponding to V_{k} the electrons on the adparticle and those in the solid are in the ground and in an excited state, respectively, with an excitation energy E_{k} for the latter. Thus, V_{k}(z)’s form a continuum of surface potentials filling all energies above V_{O}(z). Finally, for the adparticle ionized by removing its valence electron and the solid in the ground state, the corresponding surface potential is \({{\text{V}}_ + }{\text{(z) + }}{{\text{I}}_\infty }\) where \({I_\infty}\) - the ionization energy of the isolated particle - was explicitly singled out from the z-dependent part.

## Keywords

Morse Potential Kinetic Energy Distribution Neutralization Rate Diabatic State Desorption Yield## Preview

Unable to display preview. Download preview PDF.

## References

- 1.Desorption Induced by Electronic Transitions, DIET I, edited by N.H. Tolk, M.M. Traum, J.C. Tully and T.E. Madey ( Springer-Verlag, Berlin, 1983 ).Google Scholar
- 2.Desorption Induced by Electronic Transitions, DIET II, edited by W. Brenig and D. Menzel ( Springer-Verlag, Berlin, 1985 ).Google Scholar
- 3.E.R. Moog, J. Unguris and M.B. Webb, Surf. Sci. 134, 849 (1983).CrossRefADSGoogle Scholar
- 4.Q.J. Zhang, R. Gomer and D.R. Boman, Surf. Sci. 129, 535 (1983).CrossRefADSGoogle Scholar
- 5.P. Feulner, D. Menzel, H.J. Kreuzer and Z.W. Gortel, Phys. Rev. Lett. 53, 671 (1984).CrossRefADSGoogle Scholar
- 6.P. Feulner, in Ref. 2, pp. 142–151.Google Scholar
- 7.Z.W. Gortel, H.J. Kreuzer, P. Feulner and D. Menzel, Phys. Rev. B 35, (in print, June 1987 ).Google Scholar
- 8.P.R. Antoniewicz, Phys. Rev. B 21, 3811 (1980).CrossRefADSGoogle Scholar
- 9.C. Munde1, M. Berman and W. Domcke, Phys. Rev. B 32, 181 (1985).ADSGoogle Scholar
- 10.W. Brenig, Z. Phys. B 23, 361 (1976).CrossRefADSGoogle Scholar
- 11.N. Ernst, W. Drachsel, Y. Li, J.H. Block and H.J. Kreuzer, Phys. Rev. Lett. 57, 394 (1986).CrossRefGoogle Scholar
- 12.H.D. Hagstrum, in: Electron and Ion Spectroscopy of Solids, edited by L. Fiermans, J. Vennick and W. Dekeyser ( Plenum, New York, 1978 ).Google Scholar