Abstract
A theory of the difference in photoemission from a solid with and without a chemisorbed atom is presented. The final electron state is taken as a plane wave, damped to simulate the finite mean free path. The matrix of the spectral density function is obtained from the Hartree-Fock theory of chemisorption developed by Grimley and Pisani (see abstr. A72634 of 1974). The difference photoemission has been investigated for hydrogen on (100) simple cubium and on lithium and shows the expected four lobed intensity variation characteristic of the C4v symmetry of the adsorption site. For hydrogen on lithium, the angular dependence is slight since most photoelectrons come from a well localized site below the bottom of the conduction band. The possibility of determining the adsorbate density of states from photoemission measurements is considered.