Measurement of yields for electron emission from surfaces upon impact of laser-excited Ar*(4p) and Kr*(5p) atoms

Abstract
A laser method for the determination of the electron emission coefficient gamma for the impact of slow laser-excited rare gas atoms Rg*(mp5(m+1)p 3D3) on surfaces is described. It is based on controlled partial depletion of metastable Rg*(mp5(m+1)s 3P2) atoms in a collimated beam by two-step laser photoionization in combination with saturated laser excitation of the metastable (3P2) atoms to the (3D3) level at the surface. The method simultaneously yields the coefficients gamma for the metastable Rg*(3P2) and the laser-excited Rg*(3D3) atoms. As an application, the authors report gamma values corresponding to the impact of Ar*(3P2, 3D3) and Kr*(3P2, 3D3) atoms on several gas-covered metal surfaces. The data show that the electron emission process involves Auger de-excitation and can be interpreted as Penning ionization of adsorbed molecules. Comparison of the gamma values for the four excited rare gas species shows a complex excitation energy dependence.

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