Positron impact Excitation of 21S State of Helium Atom using a Distorted Wave Method
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Date
2013-10-17
Authors
Murithi, Ndeke William
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Abstract
The study of excitation of helium atom by positron impact has drawn considerable
attention since the prediction of existence of the positron by Dirac in 1928.This is due to
the fact that the study of atomic collisions forms the basis for understanding of many
scientific phenomena in the planetary atmosphere and Astrophysical science. In this study
the excitation of helium atom to the is state by positron impact using the Distorted
Wave formula has been done. Previously, studies have been done on the above subject
both theoretically and experimentally but the results obtained disagree among
themselves. It is on this ground that this research was based. The interaction between the
charged projectile and target causes distortion to the projectile's wave functions in the
field of target and thus the Distorted Wave Method has been used to calculate the cross
sections. A computer program DWBA 1 originally written by Madison and Bartschat was
modified to perform the numerical calculations for positron-helium scattering and the
results obtained for both differential and total cross sections compared with the existing
theoretical and experimental data. This was done at incident energies between 30eY to
390eY. The agreement between the present integral cross section results and the
experimental results of Sueoka and the differential cross section results obtained using
present method and other methods especially at IOOeY, 200eY and 300eY was
satisfactory. Simple analytic wave functions for both the initial and final states of helium
atom were used. In the distorted wave method the initial state static potential of helium
atom was used as the initial state distortion potential and a linear combination of initial
state static potential and the final state static potential was used as the final state
distortion potential.
Description
Department of Physics, 59p. 2013