Effect of quenching in resonant coherent excitation of hydrogen atoms scattered from LiF surfaces

In this paper we analyze theoretically the ‘‘signal background’’ observed in experimental studies of the radiative decay of hydrogen atoms following resonant coherent excitation ~RCE! in grazing collisions with a LiF surface. The radiation intensity is evaluated by treating the RCE within a time-dependent ~classicaltrajectory! quantal approach, and by assuming that the excited electronic states are quenched whenever the atom-surface distance drops below a certain ‘‘switching distance.’’ Associating the mechanism of excited-state quenching with the charge transfer to the LiF conduction band we show that the hereto unexplained signal background can be attributed to the dependence of the switching distance on the incident energy.