Nonequilibrium Processes During Fe(CO)5 Pyrolysis in a Shock Wave

Abstract

In this work the processes of nonequilibrium radiation and ionization in the weak shock waves (2 < M < 4) in argon or helium, containing a small admixture (0.1–2%) of Fe(CO)5 are experimentally studied. The spectra- and time-resolved measurements, performed using a ICCD camera (StreakStar II, LaVision GmbH) have shown, that the unresolved radiation spectra are situated in the range 400–700 nm. The maximum of the spectra lies approximately at 615 nm. The radiation appeared immediately at the propagating shock front and lasted about 8–12 μs. The following time-resolved measurements, performed using photomultipliers (at 615 ± 10 nm) and calibrated electric probes have shown intensive peaks of emission and electric current with duration of few μs, that correlates with the characteristic time of active growth of iron clusters. The analysis of the results obtained allowed to conclude that the real mechanism of generation of the observed peaks of radiation and ionization is the instant dissociation of Fe(CO)5 causing an active condensation process of a supersaturated vapor of iron atoms, which results in the formation of excited and ionized iron clusters.