Nonperturbative treatment of coupled anharmonic vibrational molecular modes analyzed by 2D-infrared spectroscopy

TL;DR

This paper presents an analytical non-perturbative approach to understanding coupled anharmonic vibrational modes in molecules using 2D-infrared spectroscopy, revealing detailed spectral structures and the influence of overtones.

Contribution

It introduces a novel analytical method for non-perturbative analysis of vibrational mode coupling and anharmonicity in 2D-infrared spectra, enhancing spectral interpretation.

Findings

Detailed spectral structures explained by mode coupling and anharmonicity.

Overtones and combination states significantly affect resonance shapes.

Conditions for improved quantitative spectral analysis are identified.

Abstract

In the present work, we give an analytical non-perturbative treatment of mode-mode coupling and anharmonicity occurring in molecular vibrational systems analyzed by 2D-infrared spectroscopy. This analytical description allows a detailed discussion of the intricate structure of the 2D-infrared spectra resulting from the contributions provided by the various possible chronological orderings of the interactions with fields due to overlaps of the pulses. The peculiar role of the vibrational overtones and other combination states on the resonance shapes is elucidated and conditions for a better quantitative analysis are discussed.