Nonequilibrium quantum solvation with a time-dependent Onsager cavity

TL;DR

This paper develops a theoretical framework for nonequilibrium quantum solvation with a time-dependent solvent environment, analyzing how shrinking or breathing Onsager spheres affect molecular dipole relaxation and response functions.

Contribution

It introduces a model with a time-dependent Onsager cavity to study nonequilibrium quantum solvation, revealing how solvent dynamics influence dipole relaxation and spectral features.

Findings

Shrinking spheres enhance dipole relaxation and increase spectral line width.

Breathing spheres can reduce damping and cause non-monotonous relaxation behavior.

Resonant suppression of damping occurs when breathing and relaxation rates are comparable.

Abstract

We formulate a theory of nonequilibrium quantum solvation in which parameters of the solvent are explicitly depending on time. We assume in a simplest approach a spherical molecular Onsager cavity with a time-dependent radius. We analyze the relaxation properties of a test molecular point dipole in a dielectric solvent and consider two cases: (i) a shrinking Onsager sphere, and, (ii) a breathing Onsager sphere. Due to the time-dependent solvent, the frequency-dependent response function of the dipole becomes time-dependent. For a shrinking Onsager sphere, the dipole relaxation is in general enhanced. This is reflected in a temporally increasing line width of the absorptive part of the response. Furthermore, the effective frequency-dependent response function shows two peaks in the absorptive part which are symmetrically shifted around the eigenfrequency. In contrast, a breathing sphere reduces damping as compared to the static sphere. Interestingly, we find a non-monotonous dependence of the relaxation rate on the breathing rate and a resonant suppression of damping when both rates are comparable. Moreover, the line width of the absorptive part of the response function is strongly reduced for times when the breathing sphere reaches its maximal extension.