Dynamics of the Water Dimer + Nitric Oxide Collision

Abstract

Collision‐induced intermolecular energy transfer and intramolecular vibrational redistribution in the collision of a water dimer and nitric oxide are studied by use of quasiclassical procedures. Intermolecular energy flow is shown to occur mainly through a direct‐mode mechanism transferring relatively large amounts in strong collisions. About a quarter of the energy initially deposited in the dimer transfers to the ground state NO, while the rest redistributes among internal motions of the collision system. The main portion of initial energy deposited in the dimer redistributes in the stretches of the donor monomer through the 1:1 resonance followed by in the bend through the 1:2 resonance. Energy transfer from the excited NO to the ground‐state dimer is equally efficient, transferring more than half the initial excitation to the donor monomer, the efficiency that is attributed to the internal modes operating as energy reservoirs. The hydrogen bond shares about 15% of the initial excitation stored in both dimer‐to‐NO and NO‐to‐dimer processes as a result of strong coupling of the hydrogen bond with the proton‐donor OH bond of the monomer. A small fraction of collisions proceeds through a complex‐mode mechanism and lead to NO dissociation, the dissociated O atom showing a propensity to form a new hydrogen bond.