Chemi-ionization reactions involving metastable helium atoms at high energy

Abstract

-Total chemi-ionization cross-sections have been measured over the 15 to 1 500 eV energy interval for collisions of He 2 1S and 2 3S metastable atoms with Ne, H2, N2, O2 and CO, using a slow ion measurement technique. With molecular targets these measurements have shown a strong energy dependence for the total ionization cross-section without dissociation. In the case of dissociative ionization an energy threshold appears, dependent on the energy defect of the reaction.

Investigation of critical parameters controlling the efficiency of associative ionization

“…Indeed, the translational energy of the reactants is partially converted into electronic energy within the transient neutral molecular complex that is formed and rearranged, with the subsequent release of an electron and a positively charged (excited or not) molecular cation. Together with Penning and dissociative ionization, AI is commonly referred to as chemi-ionization [1]. This AI process has been the subject of moderate attention in recent decades, though the very first mention dates from 1930 [2].…”

Laser-assisted collisions: Investigation of the optical collision process Na(3s)+Kr+h nu to Na(3p)+Kr in a crossed beam experiment

“…Only a small number of comparable crossed beam experiments have been reported before. These were in the first line experiments on laser-assisted ionization, such as He* +He + hv -+ He+ +He (Pradel et al 1987, Moncbicourt et al 1988. Differential cross section measurements in laser-assisted atom-atom collisions have not been reported so far.…”