A close coupling study of the bending relaxation of H2O by collision with He

We present a close coupling study of the bending relaxation of H2O by collision with He, taking explicitly into account the bending–rotation coupling within the rigid-bender close-coupling method. A 4D potential energy surface is developed based on a large grid of ab initio points calculated at the coupled-cluster single double triple level of theory. The bound states energies of the He–H2O complex are computed and found to be in excellent agreement with previous theoretical calculations. The dynamics results also compare very well with the rigid-rotor results available in the Basecol database and with experimental data for both rotational transitions and bending relaxation. The bending–rotation coupling is also demonstrated to be very efficient in increasing bending relaxation when the rotational excitation of H2O increases.