Low-energy electron-excited-atom scattering: quasi-degenerate case

Grujić, Petar; Koledin, D.

doi:10.1088/0022-3700/12/13/004

Cited by 2 publications

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“…Here D is the strength parameter of A* (GrujiC 1973), corresponding to the induced permanent dipole (or other sowce of force) in the quantum mechanical formulation (e.g. GrujiC and Koledin 1979) and rI and r2 are the electron and positron coordinates, respectively. We have adopted the adiabatic assumption that D follows the closer particle, which is in the nature of the considered configuration.…”

Section: Potentials and The Conditions Of The Validity Of The Classic...mentioning

confidence: 99%

Calculation of the threshold law for scattering of positrons on negative ions

Koledin

1990

J. Phys. B: At. Mol. Opt. Phys.

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Wannier's classical theory has been successfully applied to studies of fragmentation functions when the interaction potential was homogeneous. Here, the methods of classical mechanics are applied to cases with a non-homogeneous interaction potential. In this case an analytic solution is not available. However, the numerical solution can be fitted to an analytic expression. A system is discussed that in its final state consists of a highly excited atom, an electron and a positron (A*+e-+e+). The interaction potential consists of the Coulomb term plus monopole to quadrupole and/or polarisation terms.Near threshold, the cross section is fitted to the form U = aE". Results are given for H and He.

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Section: Potentials and The Conditions Of The Validity Of The Classic...mentioning

confidence: 99%

Calculation of the threshold law for scattering of positrons on negative ions

Koledin

1990

J. Phys. B: At. Mol. Opt. Phys.

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“…Böttcher [7], in treating n n + 1 transition cross sections for e-H scatter ing, has extensively used this peculiar feature of the degenerate channel scattering. In a previous work (Grujic and Koledin [8]), to be refered to as I, we have extended this method to the nondegenerate case, both for real and complex values of the "rotated space" angular momentum quantum num bers A. This procedure has been applied to the study of e-He(21L) low-energy scattering, in order to ex amine the accuracy of the approximation proposed.…”

Section: Introductionmentioning

confidence: 99%

Low-Energy e-He(2¹L) Scattering Calculations

Koledin

Grujić

1981

Zeitschrift Für Naturforschung A

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Cross sections for e-He(21L) scattering have been calculated in the energy range 1 ^E eV. For I > 0 partial cross sections a simple analytical method, proposed by the authors before, which is essentially an extension of Seaton's exact resonance method, has been applied. In the case 1 = 0, when a complex "angular momentum quantum number" in the rotated space appears, a matching procedure has been adopted, making use of a more realistic model potential.The results for Q(21S-21S), ^(2 1S-21P) and Q(21 P-2*P) cross sections are compared with other theoretical calculations and in the case of the elastic Q(21S-21S) cross section with the available experimental data as well.The applicability of the analytical method used in the electron-atom scattering calculations is discussed, in particular for those processes which play a dominant role in the Stark broaden ing of spectral lines from plasmas. Finally, the relevance of the present method to searching for an eventual resonant (or virtual) state near 2X S threshold has been discussed. I. IntroductionElectron-atom collision processes have been the subject of extensive experimental and theoretical studies, owing to their utmost importance in many physical systems, in particular in not too high tem perature plasmas. However, even in the case of e-H scattering, an exact analytical treatment of the complete collision phenomenon is beyond our pre sent mathematical capabilities, and a number of semianalytical, approximate methods have been de veloped (see e.g. Drukarev [1]). Employing refined numerical procedures, many of these methods are capable to provide accurate cross sections for vari ous processes (see e. g. Burke and Seaton [2]), usually at the expense of a considerable computing time consumed. On the other hand, in some applications scattering matrix elements (or the corresponding cross sections) of moderate accuracy, but in simple analytical form are needed, as is the case with the quantum theory of Stark broadening (Baranger [3]). In particular, in the expression for the halfwidth and shift of an isolated nonhydrogenic line one en counters the quantity I -Si Sr i, where $*(/> are the scattering matrix (diagonal) elements, for the elastic scattering on the initial (final) state of the transition. Since at low impact energies (these are usually met in plasmas where Reprint requests to Dr. P. Grujic, Institute of Physics, P. 0. Box 57, 11001 Belgrade, Yugoslavia. neutral species are still present) coupling with other atomic states are important (see e.g. Barnes and Peach [4]), second and higher order processes, like i -> i, i -> i" -etc., make considerable contributions to S^f) [5].One of the most powerful low-energy approxima tions for treating electron-atom (ion) scattering is the close coupling equations method. Within this approximation, the only analytically completely tractable case, to our knowledge, has been the dipole exact resonance model, due to Seaton [5], which applies to the hydrogen (degenerate) target. The principal shortcoming of the original Seaton t...

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Low-energy electron-excited-atom scattering: quasi-degenerate case

Cited by 2 publications

References 4 publications

Calculation of the threshold law for scattering of positrons on negative ions

Calculation of the threshold law for scattering of positrons on negative ions

Low-Energy e-He(2¹L) Scattering Calculations

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Low-energy electron-excited-atom scattering: quasi-degenerate case

Cited by 2 publications

References 4 publications

Calculation of the threshold law for scattering of positrons on negative ions

Calculation of the threshold law for scattering of positrons on negative ions

Low-Energy e-He(21L) Scattering Calculations

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Low-Energy e-He(2¹L) Scattering Calculations