TY - JOUR

T1 - Two components of the total ionization cross sections of atoms and molecules by electron impact

T2 - Resonant excitation and decay of the fermi electronhole system and the dipole electron transition from a bound to a free state at a binary collision

AU - Vaisburd, D. I.

AU - Evdokimov, K. E.

N1 - Funding Information:
The comparison of the measured ionization cross section of atoms and molecules by electron impact with the Bethe theoretical formula and the Lotz, Alkhazov, and Kim and Rudd empirical formulas and with the empirical formula suggested by Povyshev et al. [7] demonstrates that the formula suggested in this work best describes the experimental data. This work was supported in part by INTAS grant 01-458
Publisher Copyright:
© 2003 Plenum Publishing Corporation.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2003/11

Y1 - 2003/11

N2 - Large volume of the experimental data on the ionization cross sections of atoms and molecules by electron impact obtained by various authors using different methods is analyzed. The dependence of the ionization cross section Q on the energy of the incident electron E is described by a curve with a maximum. For E ≤ I, where I is the ionization potential, the cross section naturally vanishes. For E > I, it first increases fast, passes through a high maximum, and then monotonically decreases with increasing E. For comparatively large energies E > 100 I, the Bethe formula describes the experimental data almost exactly, but in the region of maximum I < E < 10 I, it deviates significantly from the measurement data. In the present paper it has been established that the experimental dependence Q(E) in the region of maximum is well described by a resonant curve similar to Lorentz distribution. It is assumed that the main contribution to the atomic ionization by a slow electron comes from the resonant excitation and the decay of the Fermi electron-hole system. An empirical formula for the cross section of atom ionization by electron impact Q(E) is suggested which takes into account resonance for incident electrons of small energies and is transformed into the Bethe formula for large E. The parameters of the formula for the ionization cross section are calculated by the least-squares method for H, He, Ne, Ar, C, N, O, Li, Na, H2, N2, O2, K-shells of C, N, Ne, Ar, K, Ca, Rb, and Sr atoms and molecules. A comparison of the experimental dependences of the ionization cross section on the energy of the incident electron with the Bethe theoretical formula and empirical formulas suggested by Lotz, Alkhazov, Kim and Rudd, and Povyshev et al. demonstrates that the formula suggested in the present paper describes the available experimental data better than others.

AB - Large volume of the experimental data on the ionization cross sections of atoms and molecules by electron impact obtained by various authors using different methods is analyzed. The dependence of the ionization cross section Q on the energy of the incident electron E is described by a curve with a maximum. For E ≤ I, where I is the ionization potential, the cross section naturally vanishes. For E > I, it first increases fast, passes through a high maximum, and then monotonically decreases with increasing E. For comparatively large energies E > 100 I, the Bethe formula describes the experimental data almost exactly, but in the region of maximum I < E < 10 I, it deviates significantly from the measurement data. In the present paper it has been established that the experimental dependence Q(E) in the region of maximum is well described by a resonant curve similar to Lorentz distribution. It is assumed that the main contribution to the atomic ionization by a slow electron comes from the resonant excitation and the decay of the Fermi electron-hole system. An empirical formula for the cross section of atom ionization by electron impact Q(E) is suggested which takes into account resonance for incident electrons of small energies and is transformed into the Bethe formula for large E. The parameters of the formula for the ionization cross section are calculated by the least-squares method for H, He, Ne, Ar, C, N, O, Li, Na, H2, N2, O2, K-shells of C, N, Ne, Ar, K, Ca, Rb, and Sr atoms and molecules. A comparison of the experimental dependences of the ionization cross section on the energy of the incident electron with the Bethe theoretical formula and empirical formulas suggested by Lotz, Alkhazov, Kim and Rudd, and Povyshev et al. demonstrates that the formula suggested in the present paper describes the available experimental data better than others.

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U2 - 10.1023/B:RUPJ.0000024368.93924.a7

DO - 10.1023/B:RUPJ.0000024368.93924.a7

M3 - Article

AN - SCOPUS:54749126751

VL - 46

SP - 1160

EP - 1173

JO - Russian Physics Journal

JF - Russian Physics Journal

SN - 1064-8887

IS - 11

ER -