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Published January 15, 1968 | public
Journal Article Open

Differences in the Angular Dependencies of Spin- and Symmetry-Forbidden Excitation Cross Sections by Low-Energy Electron Impact Spectroscopy


Optically forbidden electronic transitions can be produced by low-energy electron impact. Recent experimental investigations of helium (1-3) have shown that the differential scattering cross sections for forbidden excitations are generally enhanced relative to those for allowed ones at low incident energies and large scattering angles. We have now observed marked differences in the angular and energy dependencies of differential cross sections for various kinds of forbidden (spin, symmetry, or both) transitions in helium at low incident energies. Such differences may well provide a basis for determining the nature of optically forbidden transitions detected by electron-impact spectroscopy in other atoms and molecules.

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©1968 American Institute of Physics. Received 30 October 1967. Supported in part by the U.S. Atomic Energy Commission, Report Code No. CALT-532-16. Work performed [by J.K.R.] in partial fulfillment of the requirements for the Ph.D. in Chemistry at the California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09272002-155546 Gates and Crellin Laboratories of Chemistry, Contribution No. 3592.


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