Terminal distributions of rotational energy in free jets of CO2 by infrared emission spectrometry

Abstract

By means of Fourier transform infrared spectrometry we have analyzed the radiation from supersonic free jets of CO₂ issuing from heated nozzle sources. The terminal rotational energy contents deduced from the spectra are consistent with those obtained by other methods. The distributions of this energy are clearly non‐Boltzmann. A two‐temperature model provides remarkably faithful descriptions of the observed distributions and leads to a simple characterization of the departure from rotational equilibrium in terms of a rotational entrophy. The results show that the extent of thls departure increases with increasing source density. Competition between rotation‐rotation and rotation‐translation exchanges seems to provide a plausible explanation for the observed behavior.