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Published on: May 27, 2018
Bending Relaxation of H2 O by Collision with Para- and Ortho-H2
Ricardo Manuel García-Vázquez1, Alexandre Faure2, Thierry Stoecklin1
1UMR5255-CNRS, Université de Bordeaux, 351 cours de la libération, F-33405, Talence, France.
Abstract:
We extend our recent theoretical work on the bending relaxation of H2 O in collisions with H2 by including the three water modes of vibration coupled with rotation, as well as the rotation of H2 . Our full quantum close-coupling method (excluding the H2 vibration) is combined with a high-accuracy nine-dimensional potential energy surface. The collisions of para-H2 O and ortho-H2 O with the two spin modifications of H2 are considered and compared for several initial states of H2 O. The convergence of the results as a function of the size of the rotational basis set of the two colliders is discussed. In particular, near-resonant energy transfer between H2 O and H2 is found to control the vibrational relaxation process, with a dominant contribution of transitions with = , and being respectively the H2 initial and final rotational quantum numbers. Finally, the calculated value of the H2 O bending relaxation rate coefficient at 295 K is found to be in excellent agreement with its experimental estimate.
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