| 1. |
- Derevianko, A, et al.
(författare)
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Electric-octupole and pure-electric-quadrupole effects in soft-X-ray photoemission
- 2000
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Ingår i: Physical Review Letters. - 0031-9007. ; 84:10, s. 2116-2119
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Tidskriftsartikel (refereegranskat)abstract
- Second-order [O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms;Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.
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| 2. |
- Dias, E.W.B, et al.
(författare)
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Breakdown of the independent particle approximation in high-energy photoionization
- 1997
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Ingår i: Physical Review Letters. - 0031-9007. ; 78:24, s. 4553-4556
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Tidskriftsartikel (refereegranskat)abstract
- The independent particle approximation is shown to break down for the photoionization of both inner and outer nl (l > 0) electrons of all atoms, at high enough energy, owing to interchannel interactions with the nearby ns photoionization channels. The effect is illustrated for Ne 2p in the 1 keV photon energy range through a comparison of theory and experiment. The implications for x-ray photoelectron spectroscopy of molecules and condensed matter are discussed.
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| 3. |
- Hemmers, O, et al.
(författare)
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Beyond the dipole approximation: angular-distribution effects in valence photoemission
- 1997
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 30:21, s. L727-L733
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Tidskriftsartikel (refereegranskat)abstract
- Angular distributions of valence photoelectrons showing effects due to highermultipole photon interactions have been measured for the first time. Neon 2s and 2p photoemission exhibits effects beyond the dipole approximation throughout the 250 to 1200 eV photon-energy range studied. The results suggest that any photoemission experiment, on any sample, can be affected at relatively low photon energies, pointing to a general need for caution in interpreting angle-resolved-photoemission measurements.
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| 4. |
- Hemmers, O., et al.
(författare)
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Dipole and nondipole angular-distribution effects in valence photoemission from neon
- 2002
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 123:2-3, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Nondipole angular-distribution parameters γ and δ for neon 2s and 2p photoelectrons have been measured and are compared to all available theoretical data. The agreement is very good throughout the 150-1200 eV photon-energy range studied. Furthermore, the neon 2p dipole angular-distribution parameter β and the 2s to 2p cross-section ratio have been measured throughout the same photon-energy range. The agreement between theoretical data and experiment is excellent.
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| 5. |
- Hemmers, O, et al.
(författare)
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High-resolution electron time-of-flight apparatus for the soft X-ray region
- 1998
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Ingår i: Review of Scientific Instruments. - 0034-6748. ; 69:11, s. 3809-3817
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Tidskriftsartikel (refereegranskat)abstract
- A gas-phase time-of-flight (TOF) apparatus, capable of supporting as many as six electron-TOF analyzers viewing the same interaction region, has been developed to measure energy- and angle-resolved electrons with kinetic energies up to 5 keV. Each analyzer includes a newly designed lens system that can retard electrons to about 2% of their initial kinetic energy without significant loss of transmission; the analyzers can thus achieve a resolving power (E/Delta_E) greater than 10(4) over a wide kinetic-energy range. Such high resolving power is comparable to the photon energy resolution of state-of-the-art synchrotron-radiation beamlines in the soft x-ray range, opening the TOF technique to numerous high-resolution applications. In addition, the angular placement of the analyzers, by design, permits detailed studies of nondipolar angular distribution effects in gas-phase photoemission.
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| 6. |
- Levin, J.C., et al.
(författare)
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Production of very cold, highly charged ions by synchrotron radiation: Comparisons of the “scalpel” and “hammer” methods
- 1987
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 262:1, s. 106-109
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of kinetic energies of highy charged argon ions produced by inner-shell photoionization and by ion-beam impact have been made using time-of-flight techniques. High-charge-state recoil ions produced by beams of ∼ 0.5-1 MeV/u Cl5+ are found to have energies one to two orders of magnitude higher than ions of the same charge produced by vacancy cascades following inner-shell photoionization by synchrotron radiation. The results may have application to the development of a very cold ion source useful for angle-resolved atomic collision studies.
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| 7. |
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| 8. |
- Short, R. T., et al.
(författare)
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Production of very-low-energy highly charged ions by synchrotron radiation
- 1986
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Ingår i: Physical Review Letters. - 1079-7114. ; 56:24, s. 2614-2617
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Tidskriftsartikel (refereegranskat)abstract
- Very-low-energy highly charged ions have been produced by use of white and monochromatic x rays from a wiggler line at the Stanford Synchrotron Radiation Laboratory to generate vacancy cascades following inner-shell photoionization. Recoil-ion energies have been determined and are shown to correspond essentially to room temperatures, even for high charge states. Promising applications to study of the interaction of stellar radiation with cold matter, to high-brightness ionsource development, to precision spectroscopy, and to angle-resolved chemical-physics reactive-scattering studies are discussed.
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| 9. |
- Wehlitz, R, et al.
(författare)
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Photon energy dependence of ionization-excitation in helium at medium energies
- 1997
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 30:2, s. L51-L58
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the photoionization-excitation-to-photoionization ratio for He(+)nl (n = 2-6) at several photon energies from 90 to 900 eV. By extrapolating these values we could determine the asymptotic high-energy ratios for He(+)nl (n = 2-5) which agree with theoretical predictions. We show that the satellite-to-main-line ratios are consistent with experimental double-to-single photoionization ratios and agree well with recent measurements.
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