The challenge of generating iron-sulfur clusters.

Free iron-sulfur cluster cations are generated by the sputtering of targets which are composed of a mixture of iron and sulfur powder and the produced cluster distributions are analyzed with a quadrupole mass spectrometer. As the iron powder is prone to the facile oxidation by air, a significant amount of oxygen in the targets is observed. Consequently, the determination of the exact cluster composition is impeded by the almost identical mass of S and O 2 . Therefore, a series of targets with different material compositions have been investigated to assist the stoichiometric assignment of the produced cluster cations and to gain insight into the influence of oxygen on the production of iron-sulfur clusters. The generation of iron-chalcogenide clusters Fe x O y S z + ( x = 2–4) is studied as a function of target composition and compared with the cluster generation by sputtering the mineral pyrite. [ABSTRACT FROM AUTHOR]