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arXiv · 1908.00809

Full-dimensional (12D) variational vibrational states of CH$_4\cdot$F$^-$: interplay of anharmonicity and tunneling

Gustavo Avila·Edit Matyus
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Abstract

The complex of a methane molecule and a fluoride anion represents a 12-dimensional (12D), four-well vibrational problem with multiple large-amplitude motions, which has challenged the quantum dynamics community for years. The present work reports vibrational band origins and tunneling splittings obtained in a full-dimensional variational vibrational computation using the GENIUSH program and the Smolyak quadrature scheme. The converged 12D vibrational band origins and tunneling splittings confirm complementary aspects of the earlier full- and reduced-dimensionality studies: (1) the tunneling splittings are smaller than 0.02 cm$^{-1}$; (2) a single-well treatment is not sufficient (except perhaps the zero-point vibration) due to a significant anharmonicity over the wells; and thus, (3) a full-dimensional treatment appears to be necessary. The present computations extend to a higher energy range than earlier work, show that the tunneling splittings increase upon vibrational excitation of the complex, and indicate non-negligible `heavy-atom' tunneling.

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Gustavo Avila, Edit Matyus. 2019-08-02. Full-dimensional (12D) variational vibrational states of CH$_4\cdot$F$^-$: interplay of anharmonicity and tunneling. https://doi.org/10.1063/1.5124532

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