skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Ab initio calculation of differential and total cross sections for the ionization of water vapor by protons

Abstract

We present both differential and total cross sections for the direct ionization of water vapor by protons in the incident energy range 0.1-100 MeV. Different theoretical models are investigated within the framework of the Born approximation in order to evaluate the influence of each pairwise Coulomb interaction term among the ejected electron, the scattered proton, and the residual ionized target in the final state. In all these models, the ground state of the water molecule is described by means of an accurate molecular wave function proposed by Moccia [J. Chem. Phys. 40, 2186 (1964)]. The results of these full ab initio quantum-mechanical treatments are compared to experimental data. Good agreement is generally observed, showing that sophisticated Born models are sufficient to explain all the experimental data, including doubly differential, singly differential, and total cross sections.

Authors:
; ;  [1];  [2]
  1. Universite Paul Verlaine-Metz, Laboratoire de Physique Moleculaire et des Collisions, ICPMB (FR 2843), Institut de Physique, 1 rue Arago, 57078 Metz Cedex 3 (France)
  2. Nuclear Physics Institute, Moscow State University, Moscow 119992 (Russian Federation)
Publication Date:
OSTI Identifier:
20982134
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevA.75.022720; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; BORN APPROXIMATION; DIFFERENTIAL CROSS SECTIONS; ELECTRONS; GROUND STATES; IONIZATION; KEV RANGE 100-1000; MEV RANGE; MOLECULES; PROTONS; QUANTUM MECHANICS; TOTAL CROSS SECTIONS; WATER; WATER VAPOR; WAVE FUNCTIONS

Citation Formats

Boudrioua, O., Champion, C., Dal Cappello, C., and Popov, Y. V.. Ab initio calculation of differential and total cross sections for the ionization of water vapor by protons. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.022720.
Boudrioua, O., Champion, C., Dal Cappello, C., & Popov, Y. V.. Ab initio calculation of differential and total cross sections for the ionization of water vapor by protons. United States. doi:10.1103/PHYSREVA.75.022720.
Boudrioua, O., Champion, C., Dal Cappello, C., and Popov, Y. V.. Thu . "Ab initio calculation of differential and total cross sections for the ionization of water vapor by protons". United States. doi:10.1103/PHYSREVA.75.022720.
@article{osti_20982134,
title = {Ab initio calculation of differential and total cross sections for the ionization of water vapor by protons},
author = {Boudrioua, O. and Champion, C. and Dal Cappello, C. and Popov, Y. V.},
abstractNote = {We present both differential and total cross sections for the direct ionization of water vapor by protons in the incident energy range 0.1-100 MeV. Different theoretical models are investigated within the framework of the Born approximation in order to evaluate the influence of each pairwise Coulomb interaction term among the ejected electron, the scattered proton, and the residual ionized target in the final state. In all these models, the ground state of the water molecule is described by means of an accurate molecular wave function proposed by Moccia [J. Chem. Phys. 40, 2186 (1964)]. The results of these full ab initio quantum-mechanical treatments are compared to experimental data. Good agreement is generally observed, showing that sophisticated Born models are sufficient to explain all the experimental data, including doubly differential, singly differential, and total cross sections.},
doi = {10.1103/PHYSREVA.75.022720},
journal = {Physical Review. A},
number = 2,
volume = 75,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • A semiempirical model of single differential cross sections (SDCS) for ionization of water vapor by fast electrons and bare ions is presented. At low secondary-electron energy, the model is based on an asymptotic expansion of the first Born approximation with coefficients, that are independent of projectile properties, evaluated from experimental photoabsorption and proton-impact ionization data. As the secondary-electron energy increases, the model converges to a binary-encounter approximation. Comparisons with measured differential, total, and dissociative cross sections for ionization of water by fast electrons are used to test the model. For primary electrons with energy greater than about 500 eV, agreementmore » with these data is generally within experimental uncertainty; however, some discrepancies of uncertain origin exist.« less
  • Cross sections, differential in the energy of secondary electrons, for ionization of methane, ammonia, and water vapor by high energy protons are presented. The results are based on a model that uses photoabsorption and ion impact ionization data to evaluate the coefficients in Bethe's asymptotic cross section for inelastic scattering of high velocity ions. Model cross sections are compared with previously published data and new data on ionization of methane and water vapor by 3.0 and 4.2 MeV protons. The simple, analytic model should be very useful in transport calculations where differential ionization cross sections over a broad range ofmore » primary and secondary energies are needed.« less
  • Cross sections for production of electrons and positive ions by proton impact on water vapor have been measured from 7--4000 keV by the transverse-field method.
  • A method for calculating total cross sections without formally including nonelastic channels is presented. The idea is to use a one channel [ital T]-matrix variational principle with a complex correlation function. The derived [ital T] matrix is therefore not unitary: Elastic scattering is calculated from [vert bar][ital T][vert bar][sup 2], but total scattering is derived from the imaginary part of [ital T] using the optical theorem. The method is applied to the spherically symmetric model of electron-hydrogen scattering. No spurious structure arises; results for [sigma][sub el] and [sigma][sub total] are in excellent agreement with calculations of Callaway and Oza. Themore » method has wide potential applicability.« less