Description of cross peaks induced by intermolecular vibrational energy transfer in two-dimensional infrared spectroscopy

TL;DR

This paper provides an analytical framework for understanding intermolecular vibrational energy transfer in two-dimensional infrared spectroscopy, focusing on cross-peak formation between dark states and active acceptor states.

Contribution

It introduces an analytical description of intermolecular vibrational energy transfer via dark combination states in 2D IR spectra, with detailed dependence analysis on molecular dynamics.

Findings

Cross peaks result from coherent transfer between dark states and active states.

The model successfully simulates experimental spectra of nitrile molecules.

Cross-peak growth depends on molecular dynamical constants.

Abstract

In the present work, the analytical description of an intermolecular vibrational energy transfer, analyzed by two dimensional infrared spectroscopy, is established. The energy transfer process takes place between the dark combination states of low frequency modes pertaining to different molecules. The appearance of the cross peaks results from coherent transfer between these combination states and an optically active state of the acceptor molecule. Such a process has recently been observed experimentally between the nitrile groups of acetonitrile-d3 and benzonitrile molecules. This molecular system will be used as a model for the simulations of their two-dimensional infrared spectra. The dependence of the cross-peak growth, which is a signature of the intermolecular energy transfer, will be discussed in detail as a function of the molecular dynamical constants.