Electron-impact ionization cross sections of atmospheric molecules
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
- Department of Chemistry, Howard University, Washington, D.C. 20059 (United States)
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0111 (United States)
A theoretical model for electron-impact total ionization cross sections, which has been found to be reliable for a wide range of molecules, is applied to molecules of interest to atmospheric science. The new theory, the binary-encounter-Bethe (BEB) model, combines the binary-encounter theory and the Bethe theory for electron-impact ionization, and uses simple theoretical data for the ground state of the target molecule, which are readily available from molecular structure codes. Total ionization cross sections of 11 molecules, CS, CS{sub 2}, COS, CH{sub 4}, H{sub 2}S, NH{sub 3}, NO{sub 2}, N{sub 2}O, O{sub 3}, S{sub 2}, and SO{sub 2}, are presented for incident electron energies from threshold to 1 keV with an average accuracy of 15{percent} or better at the cross section peak. We also found that the use of vertical ionization potentials (IPs) rather than adiabatic IPs for the lowest IPs significantly improves BEB cross sections between the threshold and cross section peak for molecules whose adiabatic and vertical IPs are different by {approximately}1 eV or more (CH{sub 4} and NH{sub 3}). The BEB cross sections are presented in a compact analytic form with a small number of constants, making the cross sections suitable for modeling applications. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 435129
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 3 Vol. 106; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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