Shock Tube Vibrational Relaxation Measurements: N2 Relaxation by H2O and the CO–N2 V–V Rate

Shock tube measurements of the rates of vibrational relaxation of N2 by H2O and the vibrational exchange between N2 and CO are described. Simultaneous measurements of H2O v2 ν2 band and CO fundamental band ir emission were performed in mixtures of 1%–10% CO+∼1% H2O+N2. Measurement of H2O emission by a calibrated optical system allowed an accurate determination of the concentration of H2O for each run. The CO emission had two, almost decoupled, regions of behavior which allowed determination of two relaxation times: Pτ NCe≈ 1.6 atm· μsec (V–V exchange relaxation time between N2 and CO) and Pτ NH≈ 1.5 atm· μsec (T–V relaxation of N2 by H2O), both for 960 〈T〈2200°K.