Relaxation of the individual vibrational levels of carbon monoxide following shock heating at 2100 K

The increases in the populations of the vibrational levels v = 1 to v = 5 in CO which is undergoing thermal vibrational relaxation at 2100 K have been monitored using a cw CO laser. The experiments have been carried out in a very narrow temperature range for mixtures of CO, Ar and He. Under these conditions the first part of the relaxation region is clearly visible, and it has been possible to compare the population growths of different vibrational levels under the same conditions. We have shown that the curve for the increase in the population of the level v = 1 with time is clearly different from those of the higher levels. It has been shown that all of the vibrational levels studied in this work on CO relax with a common vibrational temperature, as postulated in the model of Shuler and co-workers. The results reported here are qualitatively different from those presented by Chow and Greene on HI.