Charge-exchange, ionization and excitation in low-energy Li${}^{+}-$ Ar, K${}^{+}-$ Ar, and Na${}^{+}-$He collisions

Abstract

Absolute cross sections are measured for charge-exchange, ionization, and excitation within the same experimental setup for the Li${}^{+}-$Ar, K${}^{+}-$ Ar, and Na${}^{+}-$ He collisions in the ion energy range $0.5-10$ keV. Results of our measurements along with existing experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes are realized with high probabilities and electrons are predominately captured in ground states. The cross section ratio for charge exchange, ionization and excitation processes roughly attains the value $10:2:1$, respectively. The contributions of various partial inelastic channels to the total ionization cross sections are estimated and a primary mechanism for the process is defined. The energy-loss spectrum, in addition, is applied to estimate the relative contribution of different inelastic channels and to determine the mechanisms for the ionization and for some excitation processes of Ar resonance lines for the K${}^{+}-$Ar collision system. The excitation function for the helium, as well as for the sodium doublet lines for the Na${}^{+}-$He collision system, reveals some unexpected features and a mechanism to explain this observation is suggested.

15 pages, 6 figures