Two-Dimensional Terahertz Spectroscopy of Condensed-Phase Molecular Systems

TL;DR

This paper reviews the latest developments in two-dimensional terahertz spectroscopy, highlighting its ability to probe molecular vibrations, nonperturbative light-matter interactions, ionization, and electron transport in condensed-phase systems.

Contribution

It provides a comprehensive overview of 2D-THz spectroscopy concepts and recent experimental results in molecular crystals and liquids, emphasizing new insights into ultrafast molecular dynamics.

Findings

Vibrational responses in molecular crystals up to nonperturbative regimes

Observation of field-driven ionization processes in liquids

Insights into electron transport mechanisms in water

Abstract

Nonlinear terahertz (THz) spectroscopy relies on the interaction of matter with few-cycle THz pulses of electric field amplitudes up to megavolts/centimeter (MV/cm). In condensed-phase molecular systems, both resonant interactions with elementary excitations at low frequency such as intra- and intermolecular vibrations and nonresonant field-driven processes are relevant. Two-dimensional THz (2D-THz) spectroscopy is a key method for following nonequilibrium processes and dynamics of excitations to decipher the underlying interactions and molecular couplings. This article addresses the state of the art in 2D-THz spectroscopy by discussing the main concepts and illustrating them with recent results. The latter include the response of vibrational excitations in molecular crystals up to the nonperturbative regime of light-matter interaction and field-driven ionization processes and electron transport in liquid water.