Direct IR Spectroscopic Detection of a Low‐Lying Electronic State in a Metal Carbide Cluster

• Published in: Chemphyschem Vol. 19; no. 12; pp. 1424 - 1427
• Main Authors: Chernyy, Valeriy, Logemann, Remko, Kirilyuk, Andrei, Bakker, Joost M.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 19.06.2018
• Subjects: Density functional theory; Electron states; Electronic structure; Excitation; gas phase clusters; infrared action spectroscopy; Metal clusters; Tantalum; Tantalum carbide; Time dependence; gas phase clusters; infrared action spectroscopy; electronic structure
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201701365

The electronic structure of metal clusters is notoriously difficult to detect spectroscopically, due to rapid relaxation into the ground state following excitation. We have used IR multiple photon excitation to identify a low‐lying electronic state in a tantalum carbide cluster. The electronic excitation is found at 458 cm−1, and is confirmed by experiments on isotopically labeled clusters. Time‐dependent density functional theory (TD‐DFT) calculations confirm the current assignment, but a second predicted electronic state was not observed. Low detection: The energies of electronic excitations in molecules are substantially higher than those for vibrations. In metallic clusters, the rich electronic structure of the transition metal elements can bring about situations where this conventional wisdom does not hold. Here, we demonstrate the direct optical detection of one such low‐lying electronic level in a tantalum carbide cluster. The energy of the electronic excitation is so low that it is found right in the middle of the cluster's vibrational excitation.