Mapping Electronic Relaxation Dynamics In Metal Nanoclusters Using Polarization-selective Two-dimensional Electronic Spectroscopy

Jeffries, William R.

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https://hdl.handle.net/2142/116602 Copy

Description

Title

Mapping Electronic Relaxation Dynamics In Metal Nanoclusters Using Polarization-selective Two-dimensional Electronic Spectroscopy

Author(s)

Jeffries, William R.

Contributor(s)

Knappenberger, Jr., Kenneth L.

Issue Date

2022-06-22

Keyword(s)

Clusters/Complexes

Abstract

Gold monolayer protected clusters (MPCs) are a class of quantum-confined metal nanostructures that span the transition from molecular to metallic electron dynamics. MPCs are well-described by three structural motifs that include (i) an all-metal atom core, (ii) an inorganic semiring of alternating Au-S staple units, and (iii) passivating organic ligands. The structure and composition of these domains influence the nanocluster optical and electronic properties, providing a well-defined platform to elucidate structure-dependent energy relaxation mechanisms in quantum confined metals. In this presentation, ultrafast electronic and charge carrier relaxation will be discussed. Coherent two-dimensional electronic spectroscopy (2DES) provides an excitation-detection frequency-frequency correlation by spreading the transient signal over two axes that spectrally and temporally resolves state-to-state electron dynamics on the femtosecond timescale. Here, 2DES was used to distinguish several electronic fine-structure peaks that comprise a charge transfer resonance in molecular-like Au$_{38}$(SC$_{6}$H$_{13}$)$_{24}$ nanoclusters. By manipulating the polarization vector of the femtosecond pulses, additional insights on the coupling of transition dipole moments were obtained from cross-peak specific spectra. These results revealed a low-amplitude excited state absorption signal that uniquely relaxed through a charge transfer resonance within 150 femtoseconds. Evidence of population changes of excited vibrational states within the electronic manifold, which undergo intramolecular vibrational relaxation (IVR), were quantified by fitting time-dependent amplitudes of 2DES-detected cross-peaks spanning a frequency range of 1000 cm$^{-1}$. Anisotropy and orientation parameters obtained from polarization-selective 2DES were applied to better understand state-specific relaxation through coupled electronic states. Solvent dependences on charge carrier relaxation will be discussed. These results demonstrate the ability of polarization-selective 2DES to map state-resolved electron dynamics in molecular-like metal nanoclusters.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116602&&

DOI

https://doi.org/10.15278/isms.2022.WD01

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Copyright 2022 held by the authors

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