Binary-encounter-dipole model for electron-impact ionization

Journal Article · Mon Oct 31 23:00:00 EST 1994 · Physical Review A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.50.3954· OSTI ID:6947054

Kim, Y ^[1]; Rudd, M E ^[2]

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1. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
2. Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0111 (United States)

A theoretical model, which is free of adjustable or fitted parameters, for calculating electron-impact ionization cross sections for atoms and molecules is presented. This model combines the binary-encounter theory with the dipole interaction of the Bethe theory for fast incident electrons. The ratios of the contributions from distant and close collisions and interference between the direct and exchange terms are determined by using the asymptotic behaviors predicted by the Bethe theory for ionization and for stopping cross sections. Our model prescribes procedures to calculate the singly differential cross section (energy distribution) for each subshell using the binding energy, average kinetic energy, and the differential dipole oscillator strengths for that subshell. Then the singly differential cross section is integrated over the ejected electron energy to obtain the total ionization cross section. The resulting total ionization cross section near the threshold is proportional to the excess energy of the projectile electron. We found that this model yields total ionization cross sections for a variety of atoms and molecules from threshold to several keV which are in good agreement ([similar to]10% or better on average) with known experimental results. The energy distributions also exhibit the expected shapes and magnitudes. We offer a simpler version of the model that can be used when differential oscillator strengths are not known. For the ionization of ions with an open-shell configuration, we found that a minor modification of our theory greatly improves agreement with experiment.

• OSTI ID: 6947054
• Journal Information: Physical Review A; (United States), Journal Name: Physical Review A; (United States) Vol. 50:5; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOMS
BINARY ENCOUNTER METHOD
CALCULATION METHODS
COLLISIONS
CROSS SECTIONS
DIFFERENTIAL CROSS SECTIONS
ELECTRON COLLISIONS
ELECTRON-ATOM COLLISIONS
ENERGY SPECTRA
IONIZATION
MATHEMATICAL MODELS
MOLECULES
SPECTRA
TOTAL CROSS SECTIONS