Linear, third- and fifth-order nonlinear spectroscopy of a charge transfer system coupled to an underdamped vibration

TL;DR

This paper investigates how charge transfer processes in a system coupled to vibrational motion influence linear and nonlinear spectra, revealing that fifth-order spectroscopy is especially sensitive to charge transfer dynamics.

Contribution

It introduces a detailed analysis of third- and fifth-order nonlinear spectra for charge transfer systems with vibrational coupling, highlighting the unique sensitivity of fifth-order spectroscopy.

Findings

Fifth-order nonlinear response is highly sensitive to charge transfer.

Combining electron, hole, and exciton transfer produces complex spectral features.

Vibrational motion dominates the waiting time traces in 2D spectra.

Abstract

We study hole, electron and exciton transport in a charge transfer system in the presence of underdamped vibrational motion. We analyze the signature of these processes in the linear and third-, and fifth-order nonlinear electronic spectra. Calculations are performed with a numerically exact hierarchical equations of motion method for an underdamped Brownian oscillator spectral density. We find that combining electron, hole and exciton transfer can lead to non-trivial spectra with more structure than with excitonic coupling alone. Traces taken during the waiting time of a two-dimensional spectrum are dominated by vibrational motion and do not reflect the electron, hole, and exciton dynamics directly. We find that the fifth-order nonlinear response is particularly sensitive to the charge transfer process. While third-order 2D spectroscopy detects the correlation between two coherences, fifth-order 2D spectroscopy (2D population spectroscopy) is here designed to detect correlations between the excited states during two different time periods.