Reaction Dynamics of Mg(3s3p1P1) with H2

Abstract

AbstractWe measured the temperature dependence of rotational population distribution of the nascent product MgH(2∑+) in the reaction of Mg(3s3p1P1) with H2. The results indicate that the reaction is dominated by an Mg‐insertive mechanism, consistent with the isotope effect reported previously. We also presented the vibrational population distribution, and thereby found that two parallel reaction pathways are responsible for the subject reaction following Mg‐H2 collision in a bent configuration. The major one produces MgH in higher rotational levels and comparable v″ = 0 and v″ = 1 populations, while the other minor one produces MgH in low rotational levels and preferentially v″ = 0. By means of a two‐dimensional potential energy sur‐face(PES) calculation, a deep insight into the reaction pathways has been gained. The resulting PES's information reveals the possibility of a nonadiabatic transition between the excited 1B2 PES and the ground PES. The bent intermediate MgH2 near the surface crossing starts trajectories either smoothly following the dissociation coordinate of Mg‐H distance or attractively falling down through a linear HMgH geometry before breaking apart. The former trajectory accounts for the minor reaction pathway to produce MgH, while the latter one responses to the major reaction pathway. The impact of isotope and temperature effects on MgH can also be readily explained with use of the calculated PES's.