Photoelectron spectroscopy of manganese-sulfur cluster anions

Manganese-sulfur cluster anions (Mn_nS_m^-, n = 1-10, m = 1-10) have been studied using a magnetic-bottle type photoelectron spectroscopy (PES). The Mn_nS_m^- cluster anions were formed in a laser vaporization cluster source. The most stable cluster anions were found to have the compositions of n=m and n=m±1. The electron affinities of neutral manganese sulfide clusters were measured from the onsets of the PES spectra. A new electronically excited state at 0.75 eV above the ground state was found for MnS. From the size dependence of the PES spectra, it was found that Mn₂S₂^-, Mn₃S₃^-, and Mn₄S₄^- are structural frameworks in Mn_nS₂^-, Mn_nS₃^-, and Mn_nS₄^- series, respectively. The electronic properties and geometrical structures of the clusters are discussed.