An improved double-toroidal spectrometer for gas phase (e,2e) studies

A new spectrometer is described for measuring the momentum distributions of scattered electrons arising from electron-atom and electron-molecule ionization experiments. It incorporates and builds on elements from a number of previous designs, namely, a source of polarized electrons and two high-efficiency electrostatic electron energy analyzers. The analyzers each comprise a seven-element retarding-electrostatic lens system, four toroidal-sector electrodes, and a fast position-and-time-sensitive two-dimensional delay-line detector. Results are presented for the electron-impact-induced ionization of helium and the elastic scattering of electrons from argon and helium which demonstrate that high levels of momentum resolution and data-collection efficiency are achieved. Problematic aspects regarding variations in collection efficiency over the accepted momentum phase space are addressed and a methodology for their correction presented. Principles behind the present design and previous designs for electrostatic analyzers based around electrodes of toroidal-sector geometry are discussed and a framework is provided for optimizing future devices.The assistance of the AustralianGerman Research Cooperation Scheme and the Australian Research Council through Grant No. DP0452553 and a 1998 ARC RIEF grant is gratefully acknowledged

Elastic electron scattering from water vapor and ice at high momentum transfer

We compare the area, peak separation, and width of the H and O elastic peak for light and heavy water, as observed in spectra of keV electrons scattered over large angles. Peak separation is well reproduced by the theory, but the O:H area ratio is somewhat larger than expected and is equal to the O:D area ratio. Thus no anomalous scattering from H was observed. Only minor differences are observed for scattering from a gaseous or a solid target. The extracted mean kinetic energy of H and D agreed within 5% with the calculated ones for ice. For the more difficult vapor measurements agreement was on a 12% level. A preliminary attempt to extract the O kinetic energy in ice agreed within 10% with the calculated values.This work was made possible by financial support of the Australian Research Council

Historical Timeline - Centennial Celebration: The Mortola Years

The text of the speech made by Dr. Marilyn E. Weigold, Professor of History and University Historian, at a Centennial event commemorating the University’s late President and Chancellor, Dr. Edward J. Mortola, this document details the relationship between Dr. Mortola and Pace from 1947 to 1990. Dr. Mortola’s early years as Assistant Dean, Dean, Provost and Vice President are discussed and the dramatic expansion of Pace during his Presidency is highlighted. The opening of the Pleasantville campus, the founding of the School of Education, the Lienhard School of Nursing and the Law School are noted, along with the addition of innovative graduate programs and the attainment of University status. Dr. Mortola’s vision of Pace is analyzed within the context of his era and reference is made to the current Strategic Agenda

Electron spectroscopy using two-dimensional electron detection and a camera in a single electron counting mode

A brief description is given of an economical implementation of the read out of a two-dimensional detector in an electron spectrometer by a charge coupled device camera, using a pulse counting mode. Count rates up to 10 kHz can be handled in this way. A comparison with results obtained using a resistive anode detector is given for the case of electron scattering from Xe atoms. Good agreement was obtained between both detection techniques, establishing the validity of the method described here.This research was made possible by a grant of the Australian Research Council

Large-angle Electron-photon Coincidence Experiment In Atomic Hydrogen

1s-2p excitation in hydrogen has been studied by observing the angular correlation of Lyman photons detected in coincidence with inelastically scattered electrons at 54.4 eV incident energy. The electron scattering angles ranged from 10°to 133°; the results at scattering angles larger than 20°cannot be explained by currently available theories. © 1980 The American Physical Society

Plasmon-assisted electron-electron collisions at metallic surfaces

We present a theoretical treatment for the ejection of a secondary electron from a clean metallic surface induced by the impact of a fast primary electron. Assuming a direct scattering between the incident, primary electron and the electron in a metal, we calculate the electron-pair energy distributions at the surfaces of Al and Be. Different models for the screening of the electron-electron interaction are examined and the footprints of the surface and the bulk plasmon modes are determined and analyzed. The formulated theoretical approach is compared with the available experimental data on the electron-pair emission from Al.Comment: 30 pages, 9 figure

Fully Differential Cross Sections for Electron-Impact Excitation-Ionization of Aligned D₂

We examine fully differential cross sections for 176 eV electron-impact dissociative excitation-ionization of orientated D2 for transitions to final ion states 2sσg, 2pσu, and 2pπu. In previous work [Phys. Rev. A 88, 062705 (2013)PLRAAN1050-294710.1103/PhysRevA.88.062705], we calculated these cross sections using the molecular four-body distorted wave (M4DW) method with the ground-state D2 wave function being approximated by a product of two Dyson 1s-type orbitals. The theoretical results were compared with experimental measurements for five different orientations of the target molecule (four in the scattering plane and one perpendicular to the scattering plane). For the unresolved 2sσg + 2pπu final states, good agreement with experiment was found for two of the five measured orientations, and for the 2pσu final state, good agreement was found for three of the five orientations. However, theory was a factor of 200 smaller than experiment for the 2pσu state. In this paper, we investigate the importance of the approximation for the molecular ground-state wave function by repeating the M4DW calculation using a better variational wave function for the ground state

Fully differential cross-section measurements for electron-impact ionization of argon over the complete in-plane angular range

The triple differential cross section for electron-impact ionization of the 3p orbital of argon by 113.5 eV incident electrons has been measured using a magnetic angle changer in a conventional (e,2e) spectrometer. Results are presented for 2 eV ejected electrons over an extended angular range, and over the complete coplanar scattering plane for 5 eV ejected electrons. The data reveal previously unobserved structures, and are compared with recent distorted-wave Born approximation (DWBA) and hybrid DWBA R-matrix calculations. Large discrepancies exist between experiment and both calculations in the accessed regions.M. A. Stevenson and B. Lohman

Quasiparticle properties in a density functional framework

We propose a framework to construct the ground-state energy and density matrix of an N-electron system by solving selfconsistently a set of single-particle equations. The method can be viewed as a non-trivial extension of the Kohn-Sham scheme (which is embedded as a special case). It is based on separating the Green's function into a quasi-particle part and a background part, and expressing only the background part as a functional of the density matrix. The calculated single-particle energies and wave functions have a clear physical interpretation as quasiparticle energies and orbitals.Comment: 12 pages, 1 figure, to be published in Phys. Rev.