Mg+(2S) and Mg+(2P) in reaction with H2(1σ+ g): A description of the energy surfaces explaining the mechanisms

Abstract

The lowest two potential energy surfaces which involve Mg+( 2P) and Mg+(2S) atoms interacting with H2 molecules are computed to describe both the intermediate complex [MgH + 2] formed during their reactive approaches and the asymptotic outcomes of MgH+ +H or of Mg+ +H2. The calculations clearly reveal the presence of an avoided crossing between the two surfaces near the T-geometry of the complexes and the existence on the upper surface of regions where the ionic atomic states of magnesium are >coordinated> with either H2(1σ+) or H2(3 Σ+ u) states. The implications of these structural results with respect to the existing experiments in cold ion traps are discussed and shown to provide already a qualitative explanation for the final formation of MgH+/MgD + ions in the trap. In fact, a simplified treatment of the nonadiabatic coupling effects in the region of closest approach between the two Born-Oppenheimer surfaces is given via Landau-Zener curve crossing models and are found to already yield a realistic picture of the behavior seen by the experiments. © 2013 Published by Elsevier B.V.