Single- and double-electron transfer reactions of ground and metastable state Ar2+ ions

Electron transfer cross sections have been measured for reactions of Ar2+ ions with Ar, N2, O2, CO2, CH4 and C2H6. Time-of-flight techniques have been used to measure both fast neutral Ar0 and fast Ar+ products from single- and double-electron transfer processes involving Ar2+ ions with 4.0 to 7.0 keV impact energies. Incident Ar2+ ions have produced by controlled electron impact ionisation of argon atoms. Reactions have been examined as a function of ionising electron energy and cross sections determined for ground state Ar2+(3P) ions. Charge transfer cross sections have been determined to be in the range of 3*10-16 cm2 for the systems examined. Double-electron transfer cross sections are the same order of magnitude as those measured for the corresponding single-electron transfer reactions. The state distribution of the reactant ion beam has been estimated and electron transfer cross sections obtained for single- and double-electron transfer reactions of metastable Ar2+ions. The magnitudes of electron transfer cross sections in individual systems are similar for both ground and metastable state Ar2+ reactions.

Dependence of Positronium Lifetime on Temperature in Porous Materials

A positron and electron can form the bound state called positronium. When positronium is formed in a porous material, its lifetime is based on the electron density of the pore walls, temperature, and pore size according the Rectangular Extenstion to the Tao-Eldrup Model. Positronium Annihilation Lifetime Spectroscopy is an established technique of finding positronium lifetimes. Using this technique, we find positronium lifetimes at various temperatures and compare these to the expectations of the model. We find that the pore size relationship is consistent, but more data must be gathered under different conditions in order to draw conclusions about relationships between lifetime, temperature, and pore size.