Colliding beam measurements of ICR collision processes between alkali ion–atom pairs

Abstract

A colliding beam ion cyclotron resonance experiment has been developed and used to study rate constants for symmetric (resonant) and asymmetric charge exchange between potassium ion–atom pairs and between sodium ions and potassium atoms in the range of ionic energies from 0.1–2.0 eV. The results for symmetric charge exchange are in agreement with theory, but the rate constant for the exothermic process Na++K→Na+K+ at near thermal energies appears to be much larger than predicted. The changes in the ion cyclotron double resonance (ICDR) signals of ions A+, when ions B+ were heated using ICR methods, were found to be sensitive in magnitude and sign to the difference between the static field strength and the A+ ICR resonant field, as well as the intensity of the rf electric field used to heat the B+ ions. These results have been interpreted in terms of a previously published theory which takes into account explicitly the spatial distribution of ions in the ICR cell. Semiquantitative information is obtained on the energy dependence of asymmetric charge transfer between Na+ and K and resonant charge transfer between 39K+ and 41K at very low energies.