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Title:Electronic State-resolved Relaxation Dynamics In Metal Clusters Studied Using Two-dimensional Electronic Spectroscopy
Author(s):Jeffries, William R.
Contributor(s):Knappenberger, Jr., Kenneth L.; Wallace, Jordan
Subject(s):Dynamics and kinetics
Abstract:Monolayer protected nanoclusters (MPCs) are structurally-precise, quantum-confined metal nanostructures that include three structural components that influence their optical and electronic properties. These components include (i) an all-metal atom core, (ii) an organometallic semiring of alternating Au-S staples, and (iii) organic passivating ligands. The high degree of structural precision afforded by MPCs provides a well-defined platform to investigate structure-dependent energy relaxation in quantum-confined metals. In this presentation, ultrafast electronic relaxation and charge transfer dynamics will be described. Femtosecond two-dimensional electronic spectroscopy (2DES) provides spectrally resolved excitation-detection correlation maps while preserving the high time resolution of ultrafast spectroscopy by spreading the excitation-detection transient signals over two frequency axes. Here, 2DES was used to distinguish multiple electronic fine-structure states that comprise a charge-transfer resonance excited using laser pulses spanning 1.85 to 2.10 eV. These results show that electronically excited charge carriers relax through internal conversion via intramolecular vibrational relaxation (IVR) processes within 200 fs. The IVR process manifests as spectral diffusion in Au$_{38}$(SC$_{6}$H$_{13}$)$_{24}$ nanoclusters, which was monitored by resolving the excitation-detection frequency-frequency correlation function (FFCF) decay obtained from the 2DES measurements. The 2DES-detected FFCF method was applied to understand solvent dependences of the charge carriers, which undergo interfacial ligand-to-metal charge transfer, prior to thermalization. The effects of different ligands were also investigated. These results demonstrate the ability of 2DES combined with FFCF to map energy flow through nearly degenerate states, and quantify rapid internal conversion of excited charge carriers in structurally-precise metal clusters.
Issue Date:2021-06-24
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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