# Resolving State-Specific Energy Flow in Metal Nanoclusters Using 2D Electronic Spectroscopy

## TL;DR

This paper shows how 2D electronic spectroscopy can reveal how energy moves within tiny gold nanoclusters, offering new insights for photonic materials.

## Contribution

The study introduces the use of 2DES to resolve state-specific energy flow mechanisms in metal nanoclusters.

## Key findings

- 2DES resolves electronic relaxation dynamics within specific gold superatom states.
- Polarization-dependent measurements distinguish the influence of electronic state symmetry on carrier relaxation.
- Crosspeak-specific 2DES differentiates sequential relaxation from collective dynamics in nanoclusters.

## Abstract

Sub-to-few-nanometer gold nanoclusters exhibit a manifold
of electronic
states that result in nanocluster- and state-specific mechanisms of
energy flow, which present new opportunities for developing photonic
materials. Due to the spectral congestion of conventional ultrafast
transient methods, mechanistic insights into energy flow are difficult
to achieve for these systems. The use of two-dimensional electronic
spectroscopy (2DES) to resolve electronic relaxation dynamics with
state specificity for metal nanoclusters is described, along with
prospects for future research. Excitation-detection frequency correlations
inherent to 2D measurements resolve the electronic relaxation within
specific gold superatom states. The state specificity of 2DES is extended
to distinguish the influences of the electronic state symmetry on
carrier relaxation using polarization-dependent measurements. Crosspeak-specific
2DES has also been used to distinguish sequential relaxation through
nondegenerate electronic state manifolds of nanoclusters from the
collective dynamics of metallic nanoparticles. These results demonstrate
the power of 2DES for aiding the understanding of metal nanocluster
photophysical properties.