Rovibrational quantum dynamical computations for deuterated isotopologues of the methane-water dimer

TL;DR

This study computes and analyzes the rovibrational energy levels of deuterated methane-water dimers using potential energy surfaces, comparing rigid-rotor and coupled-rotors models to understand their spectral patterns.

Contribution

It provides detailed rovibrational computations for isotopologues of methane-water dimers and compares two theoretical models to interpret their energy-level structures.

Findings

Identification of rovibrational sequences with negative rotational energies

Comparison of rigid-rotor and coupled-rotors models

Insights into the spectral patterns of isotopologue dimers

Abstract

Rovibrational states of the four dimers formed by the light and the heavy isotopologues of the methane and the water molecules are computed using a potential energy surface taken from the literature. The general rovibrational energy-level pattern characteristic to all systems studied is analyzed employing two models of a dimer: the rigidly rotating complex and the coupled system of two rigidly rotating monomers. The rigid-rotor model highlights the presence of rovibrational sequences corresponding to formally negative rotational excitation energies, which is explained in terms of the coupled-rotors picture.