Electron Emission of Gas-Phase [Au25(SG)18-6H]7- Gold Cluster and Its Action Spectroscopy

A colloidal solution of Au-25(SG)(18)-protected metal gold clusters was electrosprayed [Au-25(SG)(18)-6H](7-) was selected stored in a quadrupole ion trap, and irradiated with a UV-vistunable laser. The excess charges are due to the deprotonation of six COOH moieties and a net of -1 on the Au core Photoexcitation of this species results in electron detachment. The action spectrum obtained by recording the electron detachment yield as a function of the laser wavelength displays a strong decrease as the phonon energy decreases and the onset of a band at around 650 nm. This spectrum is compared with the absorption spectrum recorded for Au-25(SG)(18) in solution. We also show that electron detachment is a one-photon process and likely involves at low photon energy, ionization by tunneling through a repulsive coulomb barrier.