PHOTOELECTRON-SPECTROSCOPY OF IRON CARBONYL CLUSTER ANIONS (FE(N)(CO)M(-), N=1-4)

Photoelectron spectra of iron-carbonyl cluster anions (Fen(CO)m-) were measured in the gas phase at the photon energy of 4.66 eV, using a magnetic bottle electron spectrometer. The iron-carbonyl cluster anions were produced by slow electron attachment of less than 1 eV to a supersonic expansion of Fe(CO)5 seeded in a He carrier gas. The photoelectron spectra of the Fen(CO)5n-1- anions show unresolved broad features, and the threshold energy (ET) and the vertical detachment energy (VDE) were determined: The ET of Fen(CO)5n-1- gradually increases by 0.1-0.3 eV with the cluster size. The study suggests that the iron carbonyl cluster anions produced are van der Waals clusters, in which Fe(CO)4- works as an ion core.