Mass spectrometric characterization of iron clusters produced by laser pyrolysis and photolysis of Fe(CO)5 in a flow reactor

Abstract

Laser-induced decomposition of iron pentacarbonyl in a flow reactor has been used to produce iron clusters and nanoparticles. The as-synthesized species are extracted from the reaction zone by a conical nozzle and expanded into the source chamber of a cluster beam apparatus where, after having traversed a differential chamber, they are analyzed in situ with a time-of-flight mass spectrometer. Three different lasers have been employed to accomplish decarbonylation of the Fe(CO)5 molecules. A pulsed CO2 laser (λ = 10.6 μm) was used to excite a mixture of SF6 and Fe(CO)5 and to pyrolyze the iron pentacarbonyl. Laser photolysis was performed by directly dissociating the Fe(CO)5 molecules with UV radiation. For this purpose, we used the tripled (λ = 355 rim) and quadrupled (λ = 266 um) Nd:YAG laser as well as an ArF excimer laser (λ = 193 nm). The mass spectrometric analysis showed that only the Nd:YAG laser produced high purity iron clusters which were essentially free of contamination.