Two photon detachment of d electrons and auger emission in photoelectron studies of Hg_n^- clusters

We report on two-photon photoelectron spectra of negatively charged mercury clusters, Hg_n^-, excited by 6.43 eV photon energy. The two-photon spectra include narrow bands attributed to inner shell d electron detachment. The position and shape of the d core detachment peaks hardly change over the size range of n = 9-280. The spectra also include broad bands, consistent with the anticipated kinetic energies of the Auger electrons. To the best of our knowledge, this is the first time that an internal-shell Auger electron has been identified in the photoelectron spectra of free metallic clusters.