Actions for Exploring the Limits of the Dipole Approximation with Angle-Resolved Electron Time-of-Flight Spectrometry [electronic resource].

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Exploring the Limits of the Dipole Approximation with Angle-Resolved Electron Time-of-Flight Spectrometry [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Science, 2002.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
65-70 : digital, PDF file
Additional Creators
United States. Department of Energy. Office of Science and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
Understanding the electronic structure of atoms and molecules is fundamental in determining their basic properties as well as the interactions that occur with different particles such as light. One such interaction is single photoionization; a process in which a photon collides with an atom or molecule and an electron with a certain kinetic energy is emitted, leaving behind a residual ion. Theoretical models of electronic structures use the dipole approximation to simplify x-ray interactions by assuming that the electromagnetic field of the radiation, expressed as a Taylor-series expansion, can be simplified by using only the first term. It has been known for some time that the dipole approximation becomes inaccurate at high photon energies, but the threshold at which this discrepancy begins is ambiguous. In order to enhance our understanding of these limitations, we measured the electron emissions of nitrogen. Beamline 8.0.1 at the Advanced Light Source was used with an electron Time-of-Flight (TOF) end station, which measures the time required for electrons emitted to travel a fixed distance. Data were collected over a broad range of photon energies (413 - 664 eV) using five analyzers rotated to 15 chamber angles. Preliminary analysis indicates that these results confirm the breakdown of the dipole approximation at photon energies well below 1 keV and that this breakdown is greatly enhanced in molecules just above the core-level ionization threshold. As a result, new theoretical models must be made that use higher order terms that were previously truncated.
Report Numbers
E 1.99:1051302
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Note
Published through SciTech Connect.
01/01/2002.
Journal of Undergraduate Research 2
Guillemin, R.; Laidman, S.; Pangilinan, J.; Yu, S.U.; Ohrwall, G.; Lindle, D.; Hemmers, O.
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