Absorption spectra of very small metal clusters exhibit individual peaks that reflect the discreteness of their localized electronic states. With increasing size, these states develop into bands and the discrete absorption peaks give way to smooth spectra with, at most, a broad localized surface-plasmon resonance band. The widely accepted view over the last decades has been that clusters of more than a few dozen atoms are large enough to have necessarily smooth spectra. Here we show through theory and experiment that for the ubiquitous thiolate cluster compound Au144(SR)60 this view has to be revised: clearly visible individual peaks pervade the full near-IR, VIS and near-UV ranges of low-temperature spectra, conveying information on quantum states in the cluster. The peaks develop well reproducibly with decreasing temperature, thereby highlighting the importance of temperature effects. Calculations using time-dependent density-functional theory indicate the contributions of different parts of the cluster-ligand compound to the spectra.
Bibliographical noteFunding Information:
H.B.E. and X.L.L. acknowledge funding from NSF-DMR-1103730 and NSF-PREM DMR-0934218. This work received computational support from the Computational System Biology Core, funded by the National Institute on Minority Health and Health Disparities (G12MD007591) from the National Institute of Health, as well as the Texas Advanced Computing Center (TACC) at the University of Texas at Austin and HPC resources from GENCI-IDRIS (Grant 2013-096829). Moreover, we acknowledge support from the European Union via the COST Action MP0903. G.R. acknowledges the support of the Western Michigan University—Faculty Research and Creative Awards. D. L. acknowledges funding from NRF of Korea (NRF-2011-0029735, NRF-2009-0093823).
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)