On-the-Fly Simulation of Two-Dimensional Fluorescence-Excitation Spectra

TL;DR

This paper introduces an on-the-fly simulation method for 2D fluorescence-excitation spectra using trajectory surface hopping, enabling detailed analysis of photoinduced dynamics in molecules.

Contribution

It develops a novel on-the-fly simulation protocol combining classical response representation with surface hopping for 2D-FLEX spectra.

Findings

Simulated 2D-FLEX spectra for pyrazine match experimental insights.

Method reveals detailed excited state dynamics.

Enables analysis comparable to attosecond spectroscopy.

Abstract

Two-dimensional (2D) fluorescence-excitation (2D-FLEX) spectroscopy is a recently proposed nonlinear femtosecond technique for the detection of photoinduced dynamics. The method records a time-resolved fluorescence signal in its excitation- and detection-frequency dependence, and hence combines the exclusive detection of excited state dynamics (fluorescence) with signals resolved in both excitation and emission frequencies (2D electronic spectroscopy). In this work, we develop an on-the-fly protocol for the simulation of 2D-FLEX spectra of molecular systems, which is based on interfacing the classical doorway-window representation of spectroscopic responses with trajectory surface hopping simulations. Applying this methodology to the gas-phase pyrazine, we show that femtosecond 2D-FLEX spectra can deliver detailed information otherwise obtainable via attosecond spectroscopy.