Ionization of atoms by electron impact (original) (raw)

Theory of electron-impact ionization of atoms

Physical Review A, 2004

The existing formulations of electron-impact ionization of a hydrogenic target suffer from a number of formal problems including an ambiguous and phase-divergent definition of the ionization amplitude. An alternative formulation of the theory is given. An integral representation for the ionization amplitude which is free of ambiguity and divergence problems is derived and is shown to have four alternative, but equivalent, forms well suited for practical calculations. The extension to amplitudes of all possible scattering processes taking place in an arbitrary three-body system follows. A well-defined conventional post form of the breakup amplitude valid for arbitrary potentials including the long-range Coulomb interaction is given. Practical approaches are based on partial-wave expansions, so the formulation is also recast in terms of partial waves and partialwave expansions of the asymptotic wave functions are presented. In particular, expansions of the asymptotic forms of the total scattering wave function, developed from both the initial and the final state, for electronimpact ionization of hydrogen are given. Finally, the utility of the present formulation is demonstrated on some well-known model problems.

Computation of electron-impact K -shell ionization cross sections of atoms

Physical Review A, 2005

The total cross sections of electron impact single K -shell ionization of atomic targets, with a wide range of atomic numbers from Z=6-50 , are evaluated in the energy range up to about 10 MeV employing the recently proposed modified version of the improved binary-encounter dipole (RQIBED) model [Uddin , Phys. Rev. A 70, 032706 (2004)], which incorporates the ionic and relativistic effects. The experimental cross sections for all targets are reproduced satisfactorily even in the relativistic energies using fixed generic values of the two parameters in the RQIBED model. The relativistic effect is found to be significant in all targets except for C, being profound in Ag and Sn.

Theoretical study of electron impact-ionization of molecules

There has been impressive progress in the area of theoretical treatments of electron impact ionization (e,2e) of atoms and molecules in the last decade. Most recently, low to intermediate incident electron energies have been reported for molecular systems. In this dissertation, different theoretical models will be used to calculate the fully differential cross section (FDCS) for (e,2e) processes for low to intermediate incident electron energies for a variety of final state electron angles and energies for the diatomic molecules H2 and N2, the triatomic molecule H2O, and the boimolecule HCOOH. In addition, there has been a large amount of interest in diatomic molecules inspired by the possibility of observing an interference effect due to the two molecular centers playing the role of a double slit. In this dissertation, the interference effect for the diatomic molecules H2 and N2 will be examined. Finally, there is presently considerable experimental effort directed towards measurin...

Electron‐Impact Ionization Cross Sections for Atoms

The Journal of Chemical Physics, 1966

Electron-impact ionization cross sections for highly ionized atoms in the hydrogen and lithium isoelectronic sequences have been computed in several variants of the Coulomb-Born and distorted-wave approximations. Electron exchange in the transition matrix element and Coulomb distortion of the partial waves were found to be important. The results are compared to recent crossed-beam experimental data and to other theoretical predictions.

Modified model for electron impact double ionization cross sections of atoms and ions

A simple modification of the semiempirical model of Shevelko et al (J. Phys. B: At. Mol. Opt. Phys. 38, 525 (2005)) is proposed for the calculation of electron impact double ionization cross section of He^0, Li^(0,1+), B^(1+), C^(1+,3+), O^(0-3+), Ar^(0-7+), Fe^(1+,3+-6+), Kr^(0-4+), Xe^(0-8+), Pr^(1+-4+), Pb^(0-9+), Bi^(1+-3+,10+), and U^(0,10+,13+) atoms and positive ions. The contributions from the direct double ionization of outer shell and indirect processes of inner shells are also considered in the proposed modification. Ionic correction and relativistic factor are also incorporated. The results of the simplified model are compared with the experimental, quantum, and other semiempirical calculations where available. It is found that the proposed modification provides better performance than those obtained by the existing semiempirical cross sections over the range of incident energies and a significant number of atomic and ionic targets considered herein for the description o...

Electron-impact ionization of atomic hydrogen

2001

Since the invention of quantum mechanics, even the simplest example of collisional breakup in a system of charged particles, e-+ H-+ H+ + e-+ e-, has stood as one of the last unsolved fundamental problems in atomic physics. A complete solution requires calculating the energies and directions for a final state in which three charged particles are moving apart. Advances in the formal description of three-body breakup have yet to lead to a viable computational method. Traditional approaches, based on two-body formalisms, have been unable to produce differential cross sections for the three-body final state. Now, by using a mathematical transformation of the Schrodinger equation that makes the final state tractable, a complete solution has finally been achieved. Under this transformation, the scattering wave function can be calculated without imposing explicit scattering boundary conditions. This approach has produced the first triple differential cross sections that agree on an absolute scale with experiment as well as the first ab initio calculations of the single differential cross section [29].

Empirical model for electron impact ionization cross sections of neutral atoms

The European Physical Journal D, 2007

A simple empirical formula is proposed for the rapid calculation of electron impact total ionization cross sections both for the open-and closed-shell neutral atoms considered in the range 1 ≤ Z ≤ 92 and the incident electron energies from threshold to about 10 4 eV. The results of the present analysis are compared with the available experimental and theoretical data. The proposed model provides a fast method for calculating fairly accurate electron impact total ionization cross sections of atoms. This model may be a prudent choice, for the practitioners in the field of applied sciences e.g. in plasma modeling, due to its simple inherent structure.

Application of Binary Encounter Approximation and Electron Impact on Ionization of Atoms

Patan Pragya, 2021

Semi-classical binary encounter approximation has been used for theoretical calculations of electron impact single ionization cross sections of Xe and Kr and double ionization of Fe atom at ground state. An accurate expression of cross section for energy transfer ΔE (σΔE) as given by Vriens and quantum mechanical Hartree-Fock velocity distributions for target electron have been used in the calculation. In the case of single ionization of Xe, 71% theoretical results lies within valid range of ratio factor less than 2 and 55% have valueless than 1.5. In the case of Kr, 97% of results have ratio factor less than 2 and 34% of results have ratio factor less than 1.1. Gryzinski and Kune model of charged particle impact double ionization of atoms found suitable for describing double ionization of atoms and ions. In the case of double ionization of Fe by electron impact 47% of results have ratio factor less than 2 and 18% of results have ratio factor 1.2. At impact 760 eV, 800 eV and 850 eV...

Electron impact ionization close to the threshold: classical calculations

Journal of Physics B: Atomic, Molecular and Optical Physics, 2003

In this paper we present Classical Trajectory Monte Carlo (CTMC) calculations for single and multiple electron ionization of Argon atoms and ions in the threshold region. We are able to recover the Wannier exponents α for the power-law behavior of the cross section σ versus excess energy: the exact value of the exponent as well as the existence of its saturation for multiple ionization appear to be related to how the total binding energy is shared between target electrons.