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[en] The relative effects of various approximations which have been proposed for the calculation of distorted-wave amplitudes have been examined using a common Hartree-Fock basis for atomic potentials and wavefunctions. For purposes of comparison, differential cross sections and angular correlation parameters for electron impact excitation of the 21P and 31P allowed transitions of helium for incident electron energies in the range 40 - 200 eV have been calculated. All of the calculations include both the direct and exchange amplitudes, and calculations were performed using both a static atomic distorting potential and a complex optical potential which included polarisation, exchange and absorption distortion in addition to the distortion of the static potential. (UK)
Journal
Journal of Physics. B, Atomic and Molecular Physics; ISSN 0022-3700; 
; v. 12(20); p. 3399-3414
; v. 12(20); p. 3399-3414
[en] Elastic and inelastic second order distorted wave (DWB2) results have been obtained for the electron-sodium problem. The theoretical calculation contains all first and second order exchange amplitudes and exchange is also included in the calculation of the distorted waves. The second order results are compared with experimental measurements and other theoretical calculations. (Author)
Source
Teubner, P.J.O.; Weigold, E. (eds.); Institute of Physics, Bristol (United Kingdom); Institute of Physics Conference Series; no. 122; 359 p; ISBN 0-85498-412-7; ; 1992; p. 49-58; Inst. of Physics; Bristol (United Kingdom); 6. International symposium on correlations and polarization in electronic and atomic collisions and (e,2e) reactions; Adelaide (Australia); 18-21 Jul 1991
; 1992; p. 49-58; Inst. of Physics; Bristol (United Kingdom); 6. International symposium on correlations and polarization in electronic and atomic collisions and (e,2e) reactions; Adelaide (Australia); 18-21 Jul 1991
[en] Second order effects are known to be important in several areas of atomic physics. In spite of the importance of second order effects, most second order calculations have reported to simplifying approximations of questionable validity. We have recently developed the capability for evaluating arbitrary second order amplitudes exactly for elastic scattering and atomic excitation by electron impact. With this capability one can evaluate second order distorted wave amplitudes for arbitrary distortion potentials and arbitrary disorder Green's functions in the interaction operator. In this paper, we will first discuss the various types of possible second order amplitudes and then we will give an overview of our results for the excitation of hydrogen by electron impact. (orig.)
Journal
Nuclear Instruments and Methods in Physics Research, Section B; ISSN 0168-583X; ; CODEN NIMBE; v. 40/41(pt.1); p. 350-353
; CODEN NIMBE; v. 40/41(pt.1); p. 350-353
[en] A new technique has been developed for evaluating second-order distorted-wave amplitudes for atomic excitation without making any approximations. By this technique, second-order amplitudes with arbitrary distorted waves and arbitrary Green's functions in the interaction can be evaluated with comparable difficulty. The utility of the method is demonstrated through a practical calculation of the second-order distorted-wave approximation for electron excitation of the 2p state of hydrogen
Journal
Physical Review Letters; ISSN 0031-9007; ; v. 53(1); p. 42-45
; v. 53(1); p. 42-45
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