Bond-forming reactivity between CF32+ and H2/D2

Abstract

The ionic products formed in collisions of CF32+ with X2 (X=H, D) are quantified as a function of the collision energy. The investigations show that, for both neutral targets, the cross-section for forming CF2+ ions from electron-transfer reactions and the cross-section for the chemical reaction forming XCF2+ increase with decreasing collision energy. This energy dependence is well reproduced by a model based on Landau–Zener theory, as are the markedly differing energy dependencies of the other reaction cross-sections which are available in the literature for molecular dication electron-transfer reactions with X2. The differing radial velocities at the curve crossing between reactant (dication+neutral) and product (monocation+X2+) potentials at a given collision energy is proposed as a possible explanation for the intermolecular isotope effect that has been detected in such electron-transfer reactions. The ratio of the cross-sections for the chemical and electron-transfer reactions following collisions of CF32+ with X2 is similar in both of the collision systems and does not vary strongly with energy. A simple model, again employing Landau–Zener theory and requiring the ab initio calculation of the structure and energetics of HCF22+, appears to qualitatively account for this energy dependence. Following collisions of CF32+ with X2 an additional “chemical” channel, forming XF+, is also detected. The markedly differing energy dependence of the cross-section for forming XCF2+ and XF+ appear to indicate that these ions are formed via independent pathways.