Energy balance and branching ratios for the chemiluminescent SiNO2 reaction: Formation of SiO a3Σ+, ν′ ⩾ 0, and ultrafast a3Σ+ −b3Π EE energy transfer

Abstract

Abstract Silicon atoms react under single collision conditions with NO2 to yield intense chemiluminescent emission from the SiO a3Σ+−X1Σ+ and b3Π−X1Σ+ intercombination band systems and weak emission from the A1Π−X1Σ+ band system While the cross section for formation of the SiO a3Σ+ and b3Π states appears to be notably greater than that for the far more exothermic Si + N2O reaction, the observed intercombination emissions from the SiNO2 reaction involve far fewer b3Π vibrational quantum levels and hence considerably less spectral overlap. This facilitates the first observation of emission from SiO a3Σ+ vibrational quantum levels, ν′ 0. Pressure-dependent studies demonstrate that the SiO A1Π and b3Π (Poxidant 0 and (3) indicates, through a comparison of single and multiple collision chemiluminescent spectra, the presence of a significant ultrafast EE transfer between the SiO a3Σ+ and b3Π states, the dominant intramolecular process corresponding to SiO a3Σ+, ν′= 3 ÷ Ar → SiO b3Π, ν = 2 + Ar.