Positron scattering and ionization of neon atoms — theoretical investigations

Abstract

Although positron scattering with inert gas atoms has been studied in theory as well as in experiment, there are discrepancies. The present work reports all the major total cross sections of e + -neon scattering at incident energies above ionization threshold, originating from a complex potential formalism. Elastic and cumulative inelastic scatterings are treated in the complex spherical e + -atom potential. Our total inelastic cross section includes positronium formation together with ionization and excitation channels in Ne. Because of the Ps formation channel it is difficult to separate out ionization cross sections from the total inelastic cross sections. An approximate method similar to electron-atom scattering has been applied to bifurcate ionization and cumulative excitation cross sections at energies from threshold to 2000 eV. Comparisons of present results with available data are made. An important outcome of this work is the relative contribution of different scattering processes, which we have shown by a bar-chart at the ionization peak.

Electron and Positron Impact Ionization Cross Sections of O and Hg Atoms

“…As far as the role of energy parameter ∆ in V abs is concerned, there is a difference between positron and electron scattering, and it arises due to the positronium formation observed with positrons [16]. With the full complex potential inserted into the Schroedinger equation, we treat it exactly in partial wave analysis by solving the corresponding first order differential equations for the real (δ R ) and the imaginary (δ I ) parts of the complex phase shift function, in order to determine Q el , Q inel , and Q T [17].…”

Optical potential approach for positron scattering by metastable 2 3 S state of helium

“…Including these channels is critical to understand collisions of positron-excited atom systems. Despite there being significant progress in theoretical descriptions of the charge transfer rearrangement process during the past decades and a number of approaches have been employed to study the Ps-formation channel for positron collisions with ground state atoms, [5][6][7][8][9][10][11][12][13][14] Ps-formation for positron scattering on excited atoms remains a challenge and the underlying physics of this process has yet to be elucidated. [1] The only available reports on the work of Ps-formation in positron-excited atom systems are the convergent close-coupling calculation (CCC) from Utamuratov et al [15] and the work of Hanssen et al, [15] in which they studied Ps-formation in excited helium using a four-body version of the continuum distorted wave approach at intermediate and high positron impact energies, which is not involved in the present work.…”

Low-energy structure in the ionization of argon: Comparison of experiment with theory

“…Understanding the motion of the electrons in strong laser fields is a fascinating issue with important implications for making new advances in attosecond physics. [1][2][3][4] When atoms are exposed to an intense laser field, the motion of the electrons can be mapped into two regimes, depending on the laser intensity and the wavelength, by using the Keldysh parameter, [5] γ = I p /(2U p ), where I p is the ionization potential of the target atom and U p is the ponderomotive energy of the electron (U p = e 2 E 2 laser /4m e ω 2 ). Particularly, if γ < 1, the tunneling ionization becomes dominant.…”