D.M. Newns

Dynamic screening in photoemission from adsorbed species

Abstract The level shift, plasmon satellites and electron-hole structure in photoemission from an adsorbate energy level are estimated within the framework of the surface response function.

Theory of adsorbate vibrational excitation by inelastic electron scattering

Abstract For electrons specularly reflected at a metal surface the differential cross-section for excitation of a single adsorbate vibration is calculated, with special application to the adsorbed CO group.

Relaxation shifts and plasmon excitation in absorption spectroscopy of adsorbed atoms

Abstract The excitation probability for surface plasmons, and the level shift due to the image force, are investigated when an electron is excited from a core level to an unoccupied virtual level of the adatom. The results differ strongly from the corresponding ones in XPS, in a manner depending on the energy variation of the width of the virtual level.

Theory of a Tm impurity in metals in a jj-coupling model

A Tm magnetic impurity with U= infinity is considered in the jj-coupling scheme in the limit of zero j.j coupling. The model has SU(N) symmetry. The spin-fluctuation energy scale is found in the f12 and f13 Kondo limits via Haldane scaling arguments. The model possesses a 1/N expansion; selecting the leading-N diagrams in perturbation theory, the Yafet-Varma integral equation is derived. This is solved analytically in the f1 and f2 Kondo limits and the results for N to infinity are found to be in accord with scaling theory. The energy separation between the singlet ground state and the N-fold-degenerate excited state is found as a function of f occupation in the large-N limit. The results are found to differ significantly with data on LaTmSe and YTmSe. A model with large j.j coupling is also considered and does not significantly improve the agreement.

Plasmon excitations of free and adsorbed thin metallic films

Abstract Starting from a simple model of a metallic layer one atom thick, the dispersion laws for plasmon-like excitations of long wavelength are given both for isolated and adsorbed layers, and compared with experiments on Cs monolayers adsorbed on tungsten.

The magnetic field dependence of the magnetization of the SU(4) and SU(6) Kondo models

Abstract The zero temperature impurity magnetization as a function of magnetic field strength has been calculated numerically for the SU(4) and SU(6) Kondo models using the integral equations derived from recent exact results for the linear dispersion model.

YbCuAl - A yardstick of progress in IV theory

Abstract The extensive data on YbCuAl is examined, on the assumption it lies close to the Kondo limit, using the results for the j = 7/2 Coqblin-Schrieffer model. Features well explained with a single parameter fit are χ(0), γ, M ( H ) curves, position of the maximum in χ( T ) and the reduction of the high T moment. The apparent success of the impurity model is discussed in the large N approach to the lattice model.

XPS satellite spectra for adsorbed atoms

Abstract The surface plasmon and electron-hole satellite spectra in core-level XPS of a large adsorbed atom are calculated for an idealised model of a metal surface.

Hydrogen chemisorption on jellium: Interpretation

Abstract The main features of first principles calculations for hydrogen chemisorption on jellium are reproduced and interpreted by a one-parameter analytic model.

Hydrogen chemisorption on jellium: A simple interpretation

Abstract Existing first principles calculations for H chemisorbed on jellium are interpreted by a simple model which reproduces the main one-body features of the results. The relationship with a picture of the H 1s orbital coupling to substrate wavefunctions is thus brought out.