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Absolute cross sections and polarization for electron-impact excitation of the resonance multiplet of the Be/sup +/ ion

Journal Article · · Phys. Rev., A; (United States)
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Crossed beams of electrons and ground state Be/sup +/ ions have been used to measure absolute cross sections for electron-impact excitation of the 313.1-nm resonance radiation corresponding to the transition Be/sup +/(2p) ..-->.. Be/sup +/(2s). Polarization fractions of the emitted light were also measured. Cross sections are absolute in the sense that all measurables including photon flux at 313 nm have been compared to relevant standards. The doublet emission cross section in units of 10/sup -16/ cm/sup 2/ can be represented as a function of electron energy by sigma=-5.10 lnE+23.0 from 4.4 to 21 eV (extrapolating to 16 x 10/sup -16/ cm/sup 2/ at the 3.96-eV threshold) and by sigma=101 lnE/E-151/E from 21 to 740 eV. Total uncertainties at a high (approximately 98%) confidence level are about +- 10%. Coulomb-Born II calculations of Bely overestimate the value at threshold by a factor of 1.7, and a recent Coulomb-Born calculation by Mann is about 10% higher at 740 eV. Two- and five-state close-coupling calculations lie, respectively, 28% and 19% above the measurement at threshold. For energies from 5 to 300 eV the measured polarization fractions can be represented by P=-0.0708 lnE+0.284 which given P=0.19 at threshold.

Research Organization:
Joint Institute for Laboratory Astrophysics, University of Colorado and National Bureau of Standards, Boulder, Colorado 80309
OSTI ID:
5239332
Journal Information:
Phys. Rev., A; (United States), Journal Name: Phys. Rev., A; (United States) Vol. 22:2; ISSN PLRAA
Country of Publication:
United States
Language:
English

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Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOMIC IONS
BEAMS
BERYLLIUM IONS
CHARGED PARTICLES
COLLISIONS
CROSS SECTIONS
ELECTRON BEAMS
ELECTRON COLLISIONS
ELECTRON-ION COLLISIONS
ENERGY-LEVEL TRANSITIONS
EXCITATION
ION BEAMS
ION COLLISIONS
IONS
LEPTON BEAMS
PARTICLE BEAMS
POLARIZATION