Published In

Physical Review A

Document Type

Article

Publication Date

5-1-1991

Subjects

Electronic excitation -- Mathematical models, Electrons -- Capture, Dispersion relations

Abstract

Results of calculations of double excitation of helium to n=2 states for fast projectiles of charge Z are presented. Nonzero Z3 contributions for single and double excitation occur only when time-ordering contributions from the second-order amplitude are nonzero. For double excitation, electron correlation must also be nonzero to obtain Z3 terms. The time-ordering effects arise from virtual off-energy-shell intermediate states. As with second-order amplitudes for Thomas singularities in electron capture, the energy-nonconserving amplitude is connected to the second-order energy-conserving amplitude by a dispersion relation. Comparison is made with experiment.

Description

This is the publisher's final PDF. Article appears in Physical Review A (http://pra.aps.org/) and is copyrighted by APS Journals (http://publish.aps.org/)

DOI

10.1103/PhysRevA.43.5184

Persistent Identifier

http://archives.pdx.edu/ds/psu/10995

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