PHOTOELECTRON-SPECTROSCOPY OF IRON-SULFUR CLUSTER ANIONS

Iron-sulfur cluster anions (FenSm-, n = 1-6, m = 1-6) have been studie d using photoelectron spectroscopy (PES) with a magnetic-bottle-type t ime-of-flight electron spectrometer. The FenSm- cluster anions were fo rmed in a laser vaporization cluster source. It was found that the sta ble cluster ions are the ones with compositions of n = m and n = m +/- 1. The electron affinities were measured from the onsets of the PES s pectra. Three low-lying electronic states were observed for FeS. The P ES spectra of FenS- (n = 1-4) series show a unique similarity, indicat ing that the Fe atom addition to FeS- has little effect on the electro nic property of FeS. The PES spectra of FenS2- series show a similarit y among the cluster anions with n = 2-4, showing that Fe2S2- is the st ructural framework of these clusters. For FenS3- series, Fe3S3- is pro posed to be the structural framework. The electronic properties and ge ometrical structures of the clusters are discussed. (C) 1996 American Institute of Physics.