A THEORETICAL-STUDY OF THE DYNAMICS OF THE REACTION OF P+ WITH AMMONIA

The dynamics of the reaction of P+ with ammonia has been studied by me ans of an approximate classical trajectory method and statistical theo ry using ab initio potential surfaces computed at relatively high leve ls of theory, including Gaussian 2 and QCISD(T) in combination with re latively large basis sets such as D95++(3df,2p), cc-pVDZ and cc-VTZ. T he trajectory computations for the capture step include the Landau-Zen er model for dealing with the electron transfer process, allow for the coupling of the orbital angular momenta of the collision with the rot ation of the reactants, and use what is thought to be a suitable repre sentation of both long and short range potentials. The observed rate c oefficient is reproduced by the most complete capture model employed a s well as the branching ratio between the two channels giving respecti vely PNH2+ + H and P + NH3+. We also predict that this branching ratio should be essentially constant with varying temperature, making the r eaction of P+ with ammonia a likely first step for the production of s mall molecules containing P-N bonds in interstellar clouds.