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Brunger, M.J.; Weigold, E.
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1993
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1993
AbstractAbstract
[en] An electron momentum spectroscopy investigation was carried out into the orbital assignment for the two bands in the 15-18 eV binding energy range of the photoelectron spectrum of the saturated, 3-member ring hydrocarbon, cyclopropane (C3H6). The present experimental momentum distributions for these states provide compelling evidence that the earlier hypothesis of Schweig and Thiel is correct. That is, the orbital assignments of these two bands are in fact opposite to the sequence of the respective ab initio eigenvalues. 11 refs., 2 figs
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Sep 1993; 8 p
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Nicholson, R.; McCarthy, I.E.; Weigold, E.; Brunger, M.J.
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre. Funding organisation: Australian Research Council, Canberra, ACT (Australia); Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1996
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre. Funding organisation: Australian Research Council, Canberra, ACT (Australia); Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1996
AbstractAbstract
[en] We highlight and examine in detail a discrepancy that exists between the results of various single-channel and multiparameter electron momentum spectroscopy (EMS) studies into the outervalence states of hydrogen fluoride (HF). In an attempt to elucidate the nature of this problem and the disagreement that exists between the best available theoretical momentum distributions (MDs), as calculated in the plane-wave-impulse-approximation with wavefunctions at the near-Hartree-Fock limit, and the most accurate experimental MDs, we have adapted a method, originally applied to extract atomic orbital information from Compton profiles to our 3σ and 1π experimental MDs. In addition we have also applied this technique to the 2s and 2p orbitals of neon, which is isoelectronic with HF, with the ramifications of the results of this investigation to HF also being outlined. (authors). 17 refs., 3 tabs., 5 figs
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Mar 1996; 13 p
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Samardzic, O.; Weigold, E.; Von Niessen, W.; Zakrzewski, V.G.; Brunger, M.J.
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1993
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1993
AbstractAbstract
[en] The complete valence shell electron separation energy spectra and momentum distributions are measured for methylamine by high resolution electron momentum spectroscopy at a total energy of 1500 eV. Many-body calculations of the separation energies and spectroscopic factors using Green's function methods are carried out and compared with the experimental data. The measured momentum distributions are compared with those calculated in the plane wave impulse approximation (PWIA) formalism using an SCF orbital wavefunction which we constructed from a basis set of states that consisted of (10s, 6p, 1d)/[5s, 3p, 1d] for the carbon and nitrogen atoms and (5s, 1p)/[3s, 1p] for each hydrogen atom. The agreement between the measured momentum distributions and the present PWIA-SCF orbital momentum distributions is, in general, fair, although for the outermost valence 7a' state the SCF wavefunction underestimates the density at low momentum. The inner valence 4a' and 3a' orbitals are found to be severely split by the final state correlation effects. The agreement between the measured and calculated spectroscopic factors and separation energies is quite good, although the measured separation energy spectra contain significant strength up to 41 eV, this strength being mainly of 4a' and 3 a' origin. 23 refs., 13 figs
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Sep 1993; 21 p
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Nicholson, R.; Braidwood, S.W.; McCathy, I.E.; Weigold, E.; Brunger, M.J.
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre. Funding organisation: Australian Research Council, Canberra, ACT (Australia); Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1996
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre. Funding organisation: Australian Research Council, Canberra, ACT (Australia); Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre1996
AbstractAbstract
[en] Momentum distributions and spectroscopic factors are obtained in a high resolution electron-momentum spectroscopy study of krypton at 1000 eV. The shapes and relative magnitudes of the momentum profiles are in good agreement with the results of calculations made within the distorted-wave impulse approximation (DWIA) framework. The DWIA describes the relative magnitudes of the 4p and 4s manifolds as well as giving a good representation of the shapes of the respective 4p and 4s cross sections. Results for the momentum profiles belonging to excited 2Po and 2Se manifolds are also presented. Spectroscopic factors for transitions belonging to the 2po and 2Se manifolds are assigned up to a binding energy of 42 eV. The spectroscopic factor for the lowest 4s transition is 0.51 ± 0.01, whereas that for the ground-state 4p transition is 0.98± 0.01. Comparisons of the present binding energies and spectroscopic factors are made against the results of several many-body calculations and photoelectron spectroscopy (PES) results. In addition, a new procedure is outlined, utilising the experimental 4p and 4s manifold cross sections, that provides information on possible initial state configuration interaction effects in krypton. 50 refs., 2 tabs., 10 figs
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Mar 1996; 23 p
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[en] Absolute differential cross sections for vibrationally elastic electron scattering from hydrogen sulphide (H2S) have been measured using a crossed electronic-molecular beam apparatus at incident energies from 1-30 eV and scattering angles between -20 and 130o. At each energy studied we have integrated our differential cross section data to obtain total elastic and elastic momentum transfer cross sections. Vibrational excitation of H2S by electron impact has also been studied at incident energies of 2 and 3 eV, in the region of the low energy shape resonance. Both our differential and integral cross sections are compared with previous experimental studies and calculated values. (author)
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Journal Article
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Numerical Data
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Journal of Physics. B, Atomic Molecular and Optical Physics; ISSN 0953-4075; ; CODEN JPAPEH; v. 26(17); p. 2913-2925
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Canney, S.; Brunger, M.J.; Storer, P.J.; Utteridge, S.; Vos, M.; Weigold, E.
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre. Funding organisation: Australian Research Council, Canberra, ACT (Australia)1996
Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre. Funding organisation: Australian Research Council, Canberra, ACT (Australia)1996
AbstractAbstract
[en] A brief overview of the (e,2e) technique as applied to solids is reported, including the spectrometer used in these studies. In particular it is described how the energy resolution of the spectrometer has been improved, by a factor of two, by the addition of an electron monochromator for production of the incident electron beam. This monochromator is also discussed in some detail. Results obtained using the monochromated beam are compared with previous data collected with a standard electron-gun source. 37 refs., 9 figs
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Mar 1996; 28 p
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AbstractAbstract
[en] The flexibility of the (e, 2e) technique in obtaining information on both structure and collision dynamics is demonstrated. An example of the structure information that can be obtained is illustrated by electron momentum spectroscopy studies on krypton, while the role of post-collision effects and correlations is explored by measurements in the autoionizing region of helium. 50 refs., 3 tabs., 4 figs
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Australia-USA advanced workshop on atomic and molecular physics; Canberra (Australia); 13-15 Feb 1995
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Conference; Numerical Data
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Brunger, M.J.; Buckman, S.J.; Newman, D.S.
Funding organisation: Australian Research Council, Canberra (Australia); Bundesministerium fuer Forschung und Technologie, Bonn (Germany, F.R.)1990
Funding organisation: Australian Research Council, Canberra (Australia); Bundesministerium fuer Forschung und Technologie, Bonn (Germany, F.R.)1990
AbstractAbstract
[en] Absolute differential and integrated total cross sections for elastic electron scattering and vibrational excitation of molecular hydrogen have been measured at an incident energy of 1.5 eV. The results are presented and discussed with particular reference to a long-standing impasse which has existed between and within experiment and theory for the near-threshold excitation of the first vibrational state of H2. The integral vibrational cross section is in good agreement (±10%) with previous beams experiments and theory but is some 60% higher than the cross section derived from a swarm analysis. 46 refs., 2 tabs., 8 figs
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Interfaces in molecular, electron and surface physics workshop; Fremantle (Australia); 4-7 Feb 1990
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Conference; Numerical Data
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AbstractAbstract
[en] There is a quite serious discrepancy in the literature, in the electron energy (E0 range 5-10 eV, between the most recent O2 elastic differential cross section (DCS) measurements particularly scattering angles of less than 60o. This disagreement is reflected in both the shape and magnitude of the respective DCSs. In order to investigate this further we have developed an apparatus which allowed us to apply the relative flow technique, for absolute elastic DCS determination, to, in this case, the e- + O2 scattering system. We found that at each of the three energies we investigated, E0 = 5, 7 and 10 eV, the present DCS results were in excellent agreement, to within the uncertainties on the measured data. (Author)
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Journal of Physics. B, Atomic, Molecular and Optical Physics; ISSN 0953-4075; ; CODEN JPAPEH; v. 30(7); p. 1813-1817
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AbstractAbstract
[en] We report measurements of absolute differential cross sections for the electron impact excitation of the υ1,3 vibrational modes of NH3 at incident energies of 5, 7.5 and 15 eV. Previous experiments have demonstrated the influence of a broad shape resonance (E symmetry) on the vibrational excitation cross section but have differed significantly as to the position and width of this feature. Consequently, we have also measured the energy dependence of the υ1,3 excitation cross section in the energy range 5-10 eV at a scattering angle of 90o. This revealed a resonance centred at about 7.3 eV with a width of approximately 3.5 eV, the latter being in good agreement with the measurement of previous authors. (Author)
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Journal of Physics. B, Atomic Molecular and Optical Physics; ISSN 0953-4075; ; CODEN JPAPE; v. 25(10); p. 2433-2440
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