Quantum study of the bending relaxation of H2O by collision with H
Vibrationally excited levels of the H2O molecule are currently detected in various environments of the interstellar medium (ISM), and collisional data for H2O, including vibration with the main colliders of the ISM, are needed. The present study focuses on the bending relaxation of H2O by collision with H when taking bending-rotation coupling explicitly into account with the rigid-bender close-coupling (RB-CC) method. With this aim, a new four-dimensional potential energy surface including the H2O bending mode is developed from a large grid of ab initio energies computed using a high level of theory. For purely rotational transitions, our RB-CC rates show very good agreement with rigid-rotor calculations performed using our new potential energy surface (PES) and with those available in the literature. Calculations for pure rotational transitions inside the excited bending level ν2 = 1 of H2O are performed and compared with their equivalents inside ν2 = 0. Vibrational quenching of H2O is also calculated and found to be much more efficient through collision with H rather than with He. © 2022 The Author(s)
A Rigid Bender Study of the Bending Relaxation of H2O and D2O by Collisions with Ar
The bending relaxation of H2O and D2O by collisions with Ar is studied at the Close Coupling level. Two new 4D PES are developed for these two systems. They are tested by performing rigid rotor calculations as well as by computing the D2O−Ar bound states. The results are compared with available theoretical and experimental data. Propensity rules for the dynamics are discussed and compared to those of H2O colliding with Ne or He. The bending relaxation cross sections and rates are then calculated for these two systems. The results are analysed and compared with available experimental data. © 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.
An explicitly correlated six-dimensional potential energy surface for the SiCSi + H2 complex
The first six-dimensional potential energy surface (PES) for the SiCSi + H2 complex is presented in this work. This surface is developed from a large number of ab initio energies computed at the explicitly correlated coupled-cluster level of theory together with the augmented correlation-consistent polarized valence triple zeta basis set (CCSD(T)-F12/aug-cc-pVTZ). These energies are fitted to an analytical function through a procedure that combines spline, least-squares, and kernel-based methods. Two minimums of similar depths were found at the equilibrium geometry of the SiCSi molecule. The dependence of the PES on the bending angle is analyzed. Furthermore, a reduced four-dimensional PES averaged over the H2 orientation is presented. Finally, the six-dimensional PES is used for computing the second virial coefficient of the SiCSi + H2 pair using classical and semi-classical methods.