Adiabatic quantum trajectory capture for cold and ultra-cold chemical reactions
Résumé
The Langevin capture model is often used to describe barrierless reactive collisions. At very low
temperatures, quantum effects may alter this simple capture image and dramatically affect the reaction
probability. In this paper, we use the trajectory-ensemble reformulation of quantum mechanics, as
recently proposed by one of the authors (Poirier) to compute adiabatic-channel capture probabilities
and cross-sections for the highly exothermic reaction Li + CaH(v = 0, j = 0)!LiH + Ca, at low and
ultra-lowtemperatures. Each captured quantum trajectory takes full account of tunneling and quantum
reflection along the radial collision coordinate. Our approach is found to be very fast and accurate,
down to extremely low temperatures. Moreover, it provides an intuitive and practical procedure
for determining the capture distance (i.e., where the capture probability is evaluated), which would
otherwise be arbitrary.