Vibrational relaxation of shock-heated N2 by atomic oxygen using the ir tracer method

Abstract

We have studied the effects of oxygen atoms on the vibrational relaxation of shock‐heated N₂ over the temperature range from 1200 to 3000 °K, using the CO tracer technique. The measured relaxation times pτN₂–O vary from 0.8 to 2 atm · μsec in this range with an uncertainty of ± 50%, in excellent agreement with existing high‐temperature shock tube and low‐temperature flow tube results. The weak temperature dependence of all these results is in marked contrast to theoretical predictions. Some limited measurements of the relaxation of CO by oxygen atoms yield values of pτ_CO–O of approximately 0.04 atm · μsec, in good agreement with other recent measurements. This rate is approximately 25 times as fast as the N₂–O rate and, coincidentally, is approximately the same as that for the relaxation of O₂ by O atoms. The greater rapidity of the CO–O and O₂–O relaxation, compared with that of N₂–O, may be the result of atom‐exchange processes in the former cases.