# Direct Readout of Excited-State Lifetimes in Chlorin Chromophores under Electronic Strong Coupling

## TL;DR

This study investigates how the excited-state lifetimes of a chlorin molecule behave under electronic strong coupling using ultrafast spectroscopy.

## Contribution

The paper introduces a novel experimental setup using dichroic Fabry-Pérot cavities to directly measure excited-state lifetimes under strong coupling.

## Key findings

- No significant changes in excited-state lifetimes were observed under electronic strong coupling conditions.
- The photophysics of Ce6T remains unchanged in cavity and free space environments.
- The results provide a benchmark for theories of cavity photochemistry.

## Abstract

The mechanisms governing
molecular photophysics under electronic
strong coupling (ESC) remain elusive to date. Here, we use ultrafast
pump–probe spectroscopy to study the excited-state relaxation
dynamics of chlorin e6 trimethyl ester (Ce6T) under strong coupling
of its transition from the electronic ground state to the Q
y
band. Ce6T is a compelling testbed with which to
address open questions about excited-state lifetimes under ESC given
prior reports of cavity-altered behavior in chlorins. We use dichroic
Fabry-Pérot cavities to provide a transparent spectral window
in which we can directly track the excited-state population following
the optical pumping of either the strongly-coupled Q
y
band or the higher-lying B band. This scheme circumvents many
of the optical artifacts inherent in ultrafast cavity measurements
and allows for facile comparison of strongly-coupled measurements
with extracavity controls. We observe no significant changes in excited-state
lifetimes for any optical pumping schemes or cavity-coupling conditions
considered herein. These results suggest that Ce6T exhibits identical
photophysics under ESC and in free space, presenting a new data point
for benchmarking emerging theories for cavity photochemistry.