Photoelectron spectra of small nanophase W metal cluster anions

We have recorded photoelectron spectra of Wn− (n=20–90) using a magnetic bottle type photoelectron spectrometer. Each photoelectron spectrum consists of a single, broad peak, shifted successively towards a higher electron binding energy (EBE) with increasing n. We estimated the threshold EBEs from the spectra. The threshold EBE versus n−1/3 plot showed a straight line and was extrapolated to 4.50 eV which is consistent with the W bulk work function, 4.55 eV. We also estimated the bond dissociation energies of Wn− cluster anions using a simple energetic model.