A Coupled Channel Method for Nuclear Scattering of Dirac Particles; High Energy Electrons on Calcium
Original Publication Date: 1976-Aug-10
Included in the Prior Art Database: 2007-Mar-30
Software Patent Institute
Mercer, Robert L.: AUTHOR [+2]
AbstractRobert L. Mercer
RC 6139 (#26466) 8/10/76
Physics (General) 23 pages
A Coupled Channel Method for Nuclear Scattering of Dirac
Particles; High Energy Electrons on Calcium
Robert L. Mercer
Computer Science Department
IBM T. J. Watson Research Center
Yorktown Heights, M.Y. 10598
Abstract: We obtain a solution of the Dirac equation in the
presence of the electromagnetic field of a complex nucleus
by means of coupled-channel partial wave analysis using a
new method in which the asymptotic solutions of the coupled
radial wave equations include all electromagnetic couplings.
Zenith, a computer program employing this method, is used to
determine the importance of dispersion effects in the
scattering of 250 MeV electrons from 40~a
and 44~a. We find
the dispersion effects to be less than one percent for angles
below 90° (i.e., considerably less than experimental error
over the range investigated experimentally), thus supporting
the view that the difference in the differential cross sections
arises primarily from a difference in the
ground state charge distributions of the two isotopes.
NUCLEAR RFACTIONS 40~a(e,e'), 44~a(e,e'),
calculations; coupled-channel calculation of dispersion
effects; energy dependence of dispersion effects.
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There arises, in the course of analyzing high energy electron-nucleus scattering experiments, the problem of determining the differential cross section given a particular charge distribution for the scattering target.' Computer codes which perform this type of analysis by means of the partial wave method have been available for many These codes, which are able to handle single-channel scattering, are adequate to the extent that the nucleus may be approximated by a static, spherically symmetric charge distribution. Therefore they have found their most fruitful applications in analyses of electron scattering from doubly or singly magic nuclei in which there are no low-lying excited states.
As the need arose to analyze data from more complex nuclei, the distorted wave Born approximation (DWBA), in which the distortion of the incoming plane wave by the Coulomb field surrounding the nucleus is correctly accounted for by the partial wave method, and nuclear distortions, etc., are treated as first-order perturbations, wa...