Abstract: The iron-sulfur cluster ions, Fe_nS_m~+(n=1-13, m=1-13), were produced by diredt laser vaporization of a solid sample containing a mixture of iron and sulfur powder. UV photodissociation of the cluster ions was studied with a tandem time-of-flight mass spectrometer. It was found that all the cluster ions with compositions of m=n, m=n-1 or m=n+5 have relatively larger abundaces, indicating that they were more stable. The photodissociation results of Fe_nS_m~+ ions showed that, when n≈m, the main channels were losses of neutral S atoms until n≈m, while for parent ions with n≈m, the main product ions have the m=n or m=n-1 compositions. Form these experimental results, it was proposed that the Fe_nS_n~+ ions might have structures similar to those of the Fe_nS_n cores in iron-sulfur proteins, while the structures of the Fe_nS_m~+ (m>n) cluster ions could be considered to have a pattern of the Fe_nS_n~+ cores with some peripheral S atoms.

Key words: Iron-surfur clusters, UV-Photodissociation, Laser vaporization, Tandem time-of-flight mass spectrometer