PHOTOIONIZATION STUDIES OF MANGANESE CLUSTERS - IONIZATION-POTENTIALSFOR MN-7 TO MN-64

The photoionization spectra of manganese clusters consisting of betwee n seven and sixty-four atoms have been measured near threshold. As for other transition metal clusters previously investigated, the ionizati on potentials (IPs) decrease rapidly but nonmonotonically up to n cong ruent to 20 and more slowly and smoothly beyond that. No correlation i s observed between Mn, IPs and their reactivity toward molecular hydro gen, reported previously by Parks et al. [J. Chem. Phys. 104, 3531 (19 96)]. In particular, the absence of any discontinuity in IP at Mn-16 s uggests that the onset of reactivity toward hydrogen noted at that siz e is not due to a sudden change in electronic structure (e.g., a nonme tal-to-metal transition), but rather to a change in cluster geometry. (C) 1997 American Institute of Physics.