Scaling and formulary of cross-sections for ion–atom impact ionization

Abstract

The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic.Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.

Alfvén ionization in an MHD-gas interactions code

“…21 The cross-section for ionization by an ion-neutral collision does not reach a value comparable to the electron-neutral collision until the velocity of the ion is comparable to that of the electron, this only occurs at energies several orders of magnitude above the ionization energy. 37,38 • Ionization proceeds only when the relative velocity between the species exceeds the threshold, critical velocity.…”

Cosmic-ray slowing down in molecular clouds: Effects of heavy nuclei

“…(17)) based on exhaustive measurements for the p + H 2 collision. For Z projectiles, Kaganovich et al (2006) give a semi-empirical fit (Eq. (82)) adjusted by a compilation of measurements.…”

“…where σ max ion (Z, E/A) is the maximum value of the cross section (Kaganovich et al 2006 Eq. (80)), which occurs at the energy E max Z (Kaganovich et al 2006 Eq.…”

US Heavy Ion Beam Research for High Energy Density Physics Applications and Fusion

“…A hybrid method has been developed for calculation of the charge-changing cross sections of ions or atoms by fast ions by combining the quasi-classical approach and the Born approximation of quantum mechanics in the regions of impact parameters in which they are valid, and summing the results to obtain the total cross section [16,17]. This approach has been tested by comparison with available experimental data and full quantum mechanical calculations.…”

“…This approach has been tested by comparison with available experimental data and full quantum mechanical calculations. A new scaling formula for the ionization and stripping cross section of atoms and ions by fully stripped projectiles has also been developed [16,18].…”