THE TUNNELLING SPLITTINGS OF THE SOME STATIONARY VIBRATIONAL STATES OF THE HYDRONIUM ANION AND RADICAL DUE TO INVERSION MOTION

Sapeshka, Uladzimir

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Title

THE TUNNELLING SPLITTINGS OF THE SOME STATIONARY VIBRATIONAL STATES OF THE HYDRONIUM ANION AND RADICAL DUE TO INVERSION MOTION

Author(s)

Sapeshka, Uladzimir

Contributor(s)

• Pitsevich, George
• Khrapunova, Aryna
• Malevich, Alex

Issue Date

2023-06-22

Keyword(s)

Vibrational structure/frequencies

Abstract

Two closely related compounds, the H₃O· radical (HR) and H₃O− anion (HA), are of significant interest in astrophysics. Both species exist as pyramidal isomers, but are not stable at room temperature. However, they can be stable at low temperatures and have been observed in interstellar space and comets. Similar to the ammonia molecule, HR and HA exist in two equivalent configurations, which makes tunneling between them possible. However, to our knowledge, no attempts have been made to calculate tunneling splittings even for the ground vibrational states of these species. In this work, a non-standard set of vibrational coordinates was utilized to describe the inversion motion. The first coordinate used was the distance (h) between the oxygen atom and the plane formed by three hydrogen atoms. The second coordinate was a fully symmetrical coordinate q₁₂₃, which was composed of three coordinates (q₁, q₂, q₃) describing the distances between valence-free hydrogen atoms. These coordinates were tested on NH₃ and H₃O⁺ species, and tunneling splittings of the ground states were obtained for both at the CCSD(T)/Aug-cc-pVQZ level of theory, yielding values of 0.78 and 53.5 cm−¹, respectively. For the HR and HA species, calculations of the two-dimensional potential energy surface (2D PES) were performed at the UHF CCSD(T)/d-aug-cc-pVQZ, UHF CCSD(T)/aug-cc-pVQZ, and CCSD(T)/aug-cc-pVQZ, CCSD(T)/d-aug-cc- pVQZ levels of theory. The calculated tunneling splittings in the ground states of the hydronium anion (4.1 cm−¹) and radical (3.4 cm−¹) were found to be significantly lower than the tunneling splitting in the ground state of the hydronium cation (53.5 cm−¹).

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122456

DOI

https://doi.org/10.15278/isms.2023.6765

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