Exploring rotation-translation coupling for a confined asymmetric rotor using molecular dynamics simulations: the case of the water molecule trapped inside a rare gas matrix

Differences between gas-phase and matrix-isolated rotational and rovibrational spectra of the water molecule are interpreted in term of the confined rotor model. The parameters of this model enable the isotopic composition of the molecule, which has non-trivial impacts on the spectra of matrix-isolated confined rotors, to be taken into account on a very simple and intuitive basis. We use molecular dynamics simulations to systematically explore the effects of the mass distribution of various isotopomers of the water molecule on the coupled rotational and translational dynamics of the confined asymmetric rotor, and on their coupling with the phonons of the argon matrix. Analysis of the trajectories reveals that, depending on the mass distribution, a preferred orientation of the water molecule can be strongly imposed by the topology of its interaction potential with the confinement medium. Features of the confining potential, and of the rotation-translation coupling, are thus revealed from classical molecular dynamics simulations.

Automated summary

The differences in rotational and rovibrational spectra of water molecules in gas-phase and matrix-isolated environments are explained using the confined rotor model. Molecular dynamics simulations show that the mass distribution of isotopomers affects the rotational and translational dynamics of confined asymmetric rotors and their coupling with argon phonons. Trajectory analysis reveals that the preferred orientation of water molecules can be strongly influenced by their interaction potential with the confinement medium, leading to insights on the confining potential and rotation-translation coupling from classical molecular dynamics simulations.