New experimental investigations of surface vibrational properties of materials with high-resolution electron energy loss spectroscopy (EELS) axe reported. This document summarizes progress over the last three year project period on surface phonon measurements on copper (001); silver (111); ultrathin magnetic films; aluminum on silicon (111); and copper-oxide based superconductors.
This project utilized high resolution electron energy loss spectroscopy to investigate chemical processes at metal surfaces. The research during the grant period being reported has been highly successful in: a) advancing the state of the art in instrumentation, b) developing lattice dynamical techniques for calculating the vibrational properties of surfaces and demonstrating the application of these techniques to structure determination, c) exploring the application of vibrational spectroscopy to novel underlayer formation occurring as a consequence of chemisorption at Al and Ti surfaces, d) examining some of the fundamental issues related to scattering mechanisms and selection rules that govern them. Our experiments have also uncovered an interesting relationship between the surface vibrational properties and the order-disorder phase transformation of W(100).
During the three year period of this grant, a major initiative was started to develop theoretical methods to treat complex open-shell atoms in a manner permitting a simple interpretation of the dynamics. This project has been far more successful than originally hoped, with accurate ground state photoionization cross sections calculated for nine different open-shell atoms in the periodic table. This work culminated in our first application to multichannel autoionizing spectra of a transition metal atom, scandium. These methods were also extended and adapted to permit a description of nonresonant two-photon processes at the perturbative level, and some nonperturbative multiphoton processes. The angular distribution of photoelectrons ejected in resonant multiphoton ionization of magnesium was also successfully calculated. We made headway toward understanding aspects of the diamagnetic quasi-Landau problem, specifically interpreting the observed simplicity of the spectrum when plotted simultaneously versus energy and field. High two-electron excitations of H− and Li− were treated using R-matrix methods, combined with a time delay analysis to quantitatively test various propensity rules proposed in the literature. These calculations also gave the first accurate description of H− experiments at Los Alamos, up to the n = 6 threshold. A new set of computer programs were developed to handle double-Rydberg ''planetary'' states of barium and strontium, incorporating long range multipole interactions explicitly. Finally, we studied triply-excited states of H−− in an attempt to clarify the question of whether such resonances exist. Each of these projects is described in greater detail below.
The various components of the high-energy physics research program at the University of Rochester are presented. (I)Fixed-target experimentation at FNAL includes studies of direct photon production by p and [pi] on H, Be, and Cu, and hybrid mesons and other physics issues in Coulomb excitation at high energies. (II)The status of the GEM (Gammas, Electrons, and Muons) Experiment at the SSC is given. (III)The D-Zero experiment at FNAL is reviewed. (IV)Deep inelastic lepton--nucleon scattering experiments are summarized: electron scattering experiments at SLAC, FNAL neutrino quad triplet runs, FNAL neutrino sign selected experiments, and SDC cosmic ray test and test beam calibration. (V)Studies of nonlinear QED at SLAC concentrated on a study of QED at critical field strength in intense laser--high-energy electron collisions. (VI)Development work on the Collider Detector at Fermilab (CDF) emphasized the CDF silicon vertex detector, the end plug calorimeter, and the SDC tile/fiber calorimetry. (VII)The theoretical physics effort is sketched.
