Showing papers by "John B. Pendry published in 1978"

The existence and detection of Rydberg states at surfaces

Abstract: It is shown that the surface barrier potential can confine electrons in surface states, which because of the coulombic tail on the potential form a Rydberg series. This previously known result is made more rigorous by a discussion of lifetime broadening of the states. Observability of the states via LEED experiments is also investigated. The Rydberg series should give rise to structure in LEED curves which can in principle be resolved for all members of the series as n to infinity .

Atomic origin of structure in EXAFS experiments

Abstract: X-ray absorption edges in solids show extended fine structure up to 30-60 Hartrees (1 or 2 keV) above the edge which is known to be caused by electron scattering from other atoms surrounding the absorbing atom. In addition other structure is sometimes observed, of a slower period, especially nearer to the edge, which are shown to be caused by scattering in the periphery of the absorbing atom. The new structure is closely related to the derivative of the p-phase shift in the case of K-shell excitation, and improved values of the phase shift can be extracted from experiment.

Theory of spin polarised photoemission from nickel

Abstract: A calculation of spin-polarised photoemission is made for a nickel (001) surface which is rigorous within the Slater-Stoner theory of ferromagnetism. The results show excellent agreement with the data of Eib and Alvarado (1976) and provide further information that this theory of ferromagnetism is a good first-order approximation in the transition metals. The possible existence of surface states and dead layers on the (001) surfaces is investigated.

Photoemission from transition metal surfaces

Abstract: Photoemission spectra for nickel are contrasted with those for copper. The differences noted are largely attributable to the short hole lifetimes in nickel-a consequence of the Fermi level falling within the band.

Theory of photoemission

Abstract: We discuss a theory of photoemission which includes multiple scattering processes, surface effects and hole-lifetimes. The important consequences of hole-lifetimes are discussed and calculations presented for three classes of materials represented by copper, nickel and aluminium.

The phase problem in LEED

Abstract: The problem of determining the phases of the diffracted waves when only their intensities can be measured is a question that has received a great deal of attention in the case of X-ray diffraction but has so far been largely ignored in low-energy electron diffraction By applying a technique similar to the one employed in the Kramers-Kronig analysis of optical reflectivity data it is found that under certain circumstances a good approximation to the phase can be found The error involved depends on the location of the zeros of the reflectivity in the complex energy plane In a test calculation for Ni (100) it is found that these zeros are favourably placed for the clean, unrelaxed surface but that any departure from this leads to a serious deterioration in the accuracy of the phase determination

Parametrised, separable potential for band structure calculations

Abstract: A new parametrisation scheme, applicable to the valence and conduction bands of solids is presented. The potential, expressed in separable form, is parametrised directly. The atomic phase shift, Green function and wavefunctions are obtained in closed form. The formalism is developed in detail and applied to the band structure of copper. It is found that the resonant d state is well approximated by a separable potential containing one free parameter, and that a two-parameter model gives a good qualitative account of s and p wave scattering from this system.

The application of the chain method to electron emission

Abstract: A method is presented of calculating emitted intensities of angular resolved emission based on the so-called 'chain method' of Pendry and Gard (1975). All final state lattice scattering effects are included in the formalism. The method is expected to have application particularly at emission energies above the normal 'Low Energy' range (0-250 eV). The method is illustrated by application to angularly resolved X-ray core level emission.