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  • 1
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    Projection-operator calculations of the lowest e(-)-He resonance (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The 1s (2s)2:2S Schulz resonance of He(-) is investigated theoretically, applying the full projection-operator formalism developed by Temkin and Bhatia (1985) in a Rayleigh-Ritz variational calculation. The technique is described in detail, and results for five different approximations of the He target state are presented in a table. Good convergence is obtained, but it is found that even the best calculated value of the resonance is about 130 meV higher than the experimentally measured value of 19.367 + or - 0.007 eV (Brunt et al., 1977), a discrepancy attributed to the contribution of the shift in the Feshbach formalism.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 34; 4591-459
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  • 2
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    Further study of a new dispersion relation for electron-atom scattering (1988)
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    Publication Date: 2011-08-19
    Description: A recently proposed dispersion relation (DR) is tested for e-He scattering; the results show that the new DR is not satisfied. Therefore, the analytic structure of the difference amplitude, previously assumed to be nonsingular, is investigated on the negative scattering energy axis. Even under severe approximations, the difference amplitude contains both poles and branch points. This suggests, however, a useful approximation of these contributions to the DR which gives very satisfactory agreement in both e-H and e-He scattering.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 37; 1415-142
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  • 3
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    Projection and quasi-projection operators for electron impact resonances on many-electron atomic targets (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A framework is established for deriving true projection operators in electron resonance calculations involving many electron targets (ions and atoms). The analytical approach is based on Feshbach's formalism the true and quasi-projection operators (QPO) one-electron systems. In the case of QPOs, the formalism is explicitly generalized to treat autoionization states lying in the region of inelastic scattering. In order to illustrate the analytical method, a recent calculation of the lowest 2P0 resonance in He is described. The application of the modified Feshbach formalism to calculation of nonresonant phase shifts in many electron systems is also discussed.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
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  • 4
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    Theory and calculation of resonances and autoionization of two-electron atoms and ions (1985)
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    Publication Date: 2011-08-19
    Description: Techniques for calculating the electron scattering from one-electron hydrogen-like targets on the basis of the Feshback formalism, are discussed. The principal similarities between resonance parameters in the Feshbach formalism and the corresponding Breit-Wigner quantities, are described in detail. Special attention is devoted to a description of the Fano line shape parameter q, and a technique for formulating it in terms of a projector operator is proposed. The theoretical methods are illustrated by numerical calculations for 1S, 3P, and 1D states of H(-) below the first excited threshold of the target atom. Calculations of 1,3S 1,3P, 1,3D states for He are also presented.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
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  • 5
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    Polarization asymmetry in two-electron photodetachment - A cogent test of the ionization threshold law (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A very sensitive test of the electron-atom ionization threshold law is suggested: for spin-aligned heavy negative ions it consists of measuring the polarization asymmetry A(PA) coming from double detachment by left- versus right-circularly polarized light. The respective yields are worked out for the Te(-) (5p)5 2P(3/2) ion. The Coulomb-dipole theory predicts A(PA) to be the ratio of two oscillating functions in sharp contrast to any power law (specifically that of Wannier, 1953) for which the ratio is expected to be a smooth function of energy.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 38; 494-496
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  • 6
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    Continuous ultraviolet absorption into double-excited states of H/-/ (1975)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Astrophysical Journal; 200; Aug. 15
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  • 7
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    A new dispersion relation for electron-atom scattering (1986)
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    Publication Date: 2011-08-19
    Description: A new forward-angle dispersion relation (DR) for electron-atom scattering is proposed. It is based on a subtraction of the static-exchange amplitude from the exact elastic scattering amplitude. Arguments are advanced to explain why this should obviate the difficulties associated with the Gerjuoy-Krall DR, specifically with the exchange Born amplitude. The new DR is tested in the elastic energy range for e-H scattering and compared with the GKDR.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Journal of Physics B - Atomic and Molecular Physics (ISSN 0022-3700); 19; L701-L70
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  • 8
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    Electron-atom spin asymmetry and two-electron photodetachment - Addenda to the Coulomb-dipole threshold law (1984)
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    Publication Date: 2011-08-19
    Description: Temkin (1982) has derived the ionization threshold law based on a Coulomb-dipole theory of the ionization process. The present investigation is concerned with a reexamination of several aspects of the Coulomb-dipole threshold law. Attention is given to the energy scale of the logarithmic denominator, the spin-asymmetry parameter, and an estimate of alpha and the energy range of validity of the threshold law, taking into account the result of the two-electron photodetachment experiment conducted by Donahue et al. (1984).
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 30; 2737-274
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  • 9
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    Electron-impact excitation of carbon and silicon in the distorted-wave approximation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The 3P to 1D electron-impact excitation cross section within the ground configuration of both neutral carbon and silicon is calculated in the distorted-wave approximation of the two-state Hartree-Fock coupled equations. An essential element of the present treatment is that orthogonality to core orbitals is not assumed in deriving equations for the scattering orbitals. A local adiabatic polarization potential is also added to the distorted-wave equations. Both elements are necessary in getting good agreement with close-coupling results for carbon to low impacting energies. The agreement is sufficiently good that predictions for silicon should be accurate to within a factor of 2.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics; vol. 15
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  • 10
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    Rotational-vibrational coupling in the theory of electron-molecule scattering (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The adiabatic-nuclei approximation of vibrational-rotational excitation of homonuclear diatomic molecules can be simply augmented to describe the vibrational-rotational coupling by including the dependence of the vibrational wave function on j. Appropriate formulas are given, and the theory, is applied to e-H2 excitation, whereby it is shown that deviations from the simple Born-Oppenheimer approximation measured by Wong and Schultz can be explained. More important, it can be seen that the inclusion of the j-dependent centrifugal term is essential for transitions involving high-rotational quantum numbers.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review Letters; 33; Oct. 21
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