FORMATION OF EXCITED HYDROGEN STATES IN STIMULATED DESORPTION FROM AN ALKALI-PROMOTED SURFACE

The desorption of hydrogen from alkali-promoted surfaces has been studied with electron-stimulated desorption. Excited hydrogen states are found for work functions that are larger than the binding energies of the corresponding atomic levels. This finding is in direct contrast with the conventional image shift of neutral atomic levels near surfaces and indicates that the levels are instead downshifted near the surface. Calculations of the energy shift and broadening of atomic hydrogen levels in the vicinity of a potassium atom chemisorbed on a metal surface confirms such a downshift. A model is presented that accounts for the observed formation of excited H in ESD from alkali-promoted surfaces. © 1990 The American Physical Society.