Dynamics of core-hole decay in adsorbates.

Abstract

Wurth and co-workers [Phys. Rev. B 35, 7741 (1987); 37, 8725 (1988)] concluded that the deexcitation-electron-spectroscopy (DES) spectra of the adsorbates become identical to the Auger-electron-spectroscopy (AES) spectra. They interpreted the double-peak structure at the higher-kinetic-energy (KE) side of the AES spectrum of the CO/Cu system as due to two different (``partly'' and ``fully'' screened) initial core-hole states. In the present Comment, the relation between the x-ray-photoelectron-spectroscopy lowest-energy state and the 1s to 2${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ resonantly excited state, and the possible mechanism by which the DES spectrum becomes very similar to the AES spectrum, are discussed. It is also proposed that the largest-KE peak of the double-peak structure corresponds to the double hole in the bonding orbital. For the CO/Cu system, the intensity of this peak is much more enhanced in comparison to the CO/Ni system because of the strong polarization of the bonding orbital toward the ligand in the presence of the core hole. The variation of the intensity of this double-peak structure reflects the degree of the polarization of the bonding orbital in the presence of the core hole.