Abstract

Theory¹ of multivalency of adsorbates on metal surfaces, taking into account the effect of the image-force stabilization measured by η² in addition to those of the electron-transfer between the adsorbate and the substrate measured by Γ and Coulomb interaction between the adsorbate electrons, has revealed that the critical lines exist in a parameter space, across which the valence charge of the adsorbate ground state changes discontinuously. Dynamical calculations² have been made on the line shapes of optical absorption and photoelectron emission spectra of a similar system. It has been found that the lines are broadened when the energy, ε_a-U_a, of the core-hole-stabilized valence level of the adsorbate goes up across the critical line at –η²/2: the broadening may be considered to be due to a short life-time of the excited neutral configuration from which an electron escapes into the substrate. The broadening of the absorption lines has been discussed in connection with the experiment of Cunningham et al³ concerning persistence or non-persistence of exciton lines in the reflection spectra of rare-gas-atoms on metal surfaces.

© 1984 Optical Society of America