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Optical Spectroscopy of the Au 4 + Cluster: The Resolved Vibronic Structure Indicates an Unexpected Isomer
Author(s) -
Förstel Marko,
Schewe Wolfgang,
Dopfer Otto
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201813094
Subject(s) - excited state , photodissociation , spectroscopy , cluster (spacecraft) , chemistry , vibronic spectroscopy , density functional theory , ground state , atomic physics , electronic structure , excited electronic state , spectral line , vibronic coupling , molecular physics , photochemistry , computational chemistry , physics , quantum mechanics , astronomy , computer science , programming language
Abstract Knowledge of the geometric and electronic structure of gold clusters and nanoparticles is vital for understanding their catalytic and photochemical properties at the molecular level. In this study, we report the vibronic optical photodissociation spectrum of cold and mass‐selected Au 4 + clusters measured at a resolution high enough to allow for comparison with Franck–Condon simulations of the excited state transitions based on time‐dependent density functional theory calculations. The three vibrational frequencies identified for the lowest‐lying optically accessible excited state at 2.17 eV stem from the Y‐shaped isomer ( C 2 v ) and not from the rhombic isomer ( D 2 h ) considered to be the ground state structure of Au 4 + . This study demonstrates that an analysis of low‐resolution electronic spectra by calculations of vertical transitions alone is not sufficient for a reliable isomer assignment of such metal clusters.