Spectroscopy and mechanism of chemiluminescent reactions between group V hydrides and ozone

Abstract

Chemiluminescence spectra are reported for the reactions of arsine, phosphine and stibine with ozone at reduced pressure. Phosphine gives rise to a visible continuum only, arsine to AsO bands and a visible continuum, and stibine apparently to SbO bands only. The species responsible for the visible continua are unknown but we suggest that they may be PO₂ and AsO₂.

At low pressures in a flow system both the visible (vis.) and discrete ultraviolet (u.v.) chemiluminescent emissions from the AsH₃+ O₃+ O₂ system increased to a maximum well downstream of the injection port. This induction period, the subsequent decay, peak and total intensities were found to be dependent on [O₃], [O₂] and pressure. A numerical kinetic model was constructed which reproduces several of the observed phenomena including a decreasing u.v./vis. ratio, decreasing u.v. and vis. intensities and increasing induction periods as [O₂] is increased. The model features a slow initiation reaction of arsine with ozone and a subsequent branched chain reaction involving the odd hydrogen radicals OH and HO₂.