Vacuum ultraviolet studies of electron impact of helium: Excitation of He n P Rydberg series and ionization-excitation of He nl Rydberg series
Laboratory measurements of the electron excitation cross sections of emission in the He Rydberg series (1sS S-1snp P) for n = 2,3,4 have been obtained. The cross sections were estimated by two methods: (1) analysis of calibrated laboratory spectra placed on an absolute scale using the H Ly dissociative excitation standard and (2) analysis of relative cross section data using a modified Born approximation. A new method has been developed for the application of the Bethe-Born approximation using experimental relative excitation functions that does not require extrapolation in a Fano plot in the determination of the absolute cross section. The two methods agree to within 3% for the 58.4 nm line when allowance is made for cascade transitions. We find the direct excitation cross sections at 200 eV for the n = 2,3,4 members of the published electron impact experimental measurements of the two electron process of ionization-excitation impact are generally in agreement, especially on the energy dependence of excitation functions, but show significant differences with theoretical calculations.
- Research Organization:
- Lunar and Planetary Laboratory, University of Arizona, Tucson
- OSTI ID:
- 6327831
- Journal Information:
- Astrophys. J.; (United States), Vol. 296:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ELECTRON-ATOM COLLISIONS
EXCITATION
HELIUM
ENERGY-LEVEL TRANSITIONS
ULTRAVIOLET SPECTRA
BORN APPROXIMATION
CROSS SECTIONS
EMISSION
IONIZATION
ATOM COLLISIONS
COLLISIONS
ELECTRON COLLISIONS
ELEMENTS
FLUIDS
GASES
NONMETALS
RARE GASES
SPECTRA
640302* - Atomic
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640304 - Atomic
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