P. S. Vinitsky

Born Series in the Theory of Electron Impact Ionization of an Atom

In this review, a generalization of few-body quantum scattering theory is given for the case of Coulomb interaction. Since in this specific case the scattering amplitude, which is a solution to a resolvent-type equation, possesses a singularity when the complex parameter z tends to the energy shell, a definition of the physical amplitude is provided. A recipe for regularizing integrals (eliminating divergences), which describe the terms of a perturbation theory series for different perturbing potentials, is formulated. As an example, the general theory is applied to the calculations of differential cross sections for a quasi-elastic electron impact ionization reaction on atomic hydrogen.

Theoretical Investigation of the p + He H + He + and p + He H + He ++ + e Reactions at Very Small Scattering Angles of Hydrogen

A hypothesis is considered that the reactions p + He → H + He+ and p + He → H + He++ + e at very small scattering angles of hydrogen can be used for the angular spectroscopy of electron correlations in a target. It is shown that this hypothesis is inconsistent.

Role of the cusp conditions in electron-helium double ionization

We develop two variational wave functions of helium which give accurate energy values and satisfy Katos cusp conditions adapted to the variational procedure. These wave functions are utilized in calculations for reproducing the electron-helium double-ionization experimental data involving both the small and large momentum transfer. A comparison of the present numerical results for the differential cross sections with experiment indicates a minor role of the cusp conditions.

Second Born effects in electron momentum spectroscopy

We present a theoretical analysis of second Born contributions to differential cross sections of electron-atom ionization processes in symmetric kinematics involving high impact energies and large momentum transfer.

(e,2e) and (e,3‐1e) studies on double processes of He near the Bethe ridge

We report (e,2e) and (e,3‐1e) experiments on the double processes of He, i.e. single ionization with simultaneous excitation and double‐ionization. The symmetric noncoplanar geometry combined with high incident electron energies has made it possible to study at large momentum transfers. The results are compared with plane wave impulse approximation (PWIA) calculations using He wavefunctions of various levels of sophistication. It is shown that shapes of the momentum dependent (e,2e) and (e,3‐1e) cross sections are well reproduced by the PWIA calculations when highly correlated wavefunctions are employed, but noticeable discrepancies between experiment and theory remain in magnitude. The discrepancies are, however, reduced with increasing impact energies, suggesting higher excitation energies may be required to analyze these double processes in terms of the PWIA.

(e,3‐1e) Reactions at Large Momentum Transfer: The Plane‐Wave Second Born Approximation

We consider theoretically symmetric (e,3‐1e) reactions in He atom at large momentum transfer. For evaluating the corresponding four‐fold differential cross sections, a theory based on the renormalized plane‐wave second Born approximation (SBA) is developed. The numerical SBA calculations for both coplanar and noncoplanar symmetric geometries are performed and compared to the experimental values.

Semiclassical model of double ionization of a helium atom

Semiclassical model of double ionization of Helium atom by fast electron based on the classical trajectories for the ejected electrons is presented. The quantities needed to fit known experimental data are calculated. Typical examples of trajectories of the ejected electrons are presented also.