Gas phase reactions of iron clusters with hydrogen. I. Kinetics

Abstract

The kinetics of the gas phase reactions of hydrogen and deuterium with iron clusters in the range Fe6 to Fe68 have been investigated. It is found that reaction rate constants are a strong function of cluster size, varying by more than five orders of magnitude in this size range. The largest rate constants correspond to approximately 3% of a hard sphere cross section. Abrupt changes in the rate constant from one cluster to the next are seen. Qualitative temperature dependencies of cluster reactivity have been determined. The more reactive clusters show decreased reactivity with increased tempeature, while the least reactive clusters become more reactive. Strong isotope effects are seen only in the Fe10 to Fe14 size range. Mechanisms for the reactions of H2 and D2 with iron clusters are discussed in light of these observations.