State-to-state inelastic rotational cross sections in five-atom systems with the MCTDH method

Abstract : We present an MCTDH method as an attractive alternative approach to the usual quantum close-coupling method which approaches some computational limits in the calculation of rotational excitation (and deexcitation) between polyatomic molecules (here collisions between triatomic and diatomic rigid molecules). We have perfomed a computational investigation of the rotational (de-)excitation of the benchmark rigid rotor H2O–H2 system on a recently developed Potential Energy Surface of the complex using the MultiConfiguration Time Dependent Hartree (MCTDH) method. We focus here on excitations and de-excitations from the 000, 111 and 110 states of H2O with H2 in its ground rotational state, looking at all the potential transitions in the energy range 1–200 cm−1. This work follows a recently completed study on the H2O-H2 cluster where we characterized its spectroscopy, and more generally serves a broader goal to describe inelastic collision processes of high dimensional systems using the MCTDH method. We find that the cross sections obtained from the MCTDH calculations are in excellent agreement with time independent calculations from previous studies, but does become challenging for the lower kinetic energy range of the de-excitation process. The MCTDH method therefore appears to be a useful complement to standard approaches to study inelastic collision for various collision partners, even at low energy, though performing better for rotational excitation than for de-excitation.
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https://hal.archives-ouvertes.fr/hal-02179642
Contributor : Aigle Clementin <>
Submitted on : Thursday, July 11, 2019 - 9:07:49 AM
Last modification on : Thursday, August 8, 2019 - 4:06:10 PM

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  • HAL Id : hal-02179642, version 1

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Steve Ndengue, Yohann Scribano, Fabien Gatti, Richard Dawes. State-to-state inelastic rotational cross sections in five-atom systems with the MCTDH method. 2019. ⟨hal-02179642⟩

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