Conformational cooling in a supersonic jet of 1,2-dichloroethane studied by matrix isolation infrared spectroscopy

Matrix isolation infrared spectroscopy has been applied to a study of conformational cooling in a supersonic jet of 1,2-dichloroethane. The conformational temperature is estimated from the intensity ratio of the infrared absorption bands for the gauche and trans conformers to be 210±10 K under a stagnation pressure of 1.0 atm. Dependence of the conformational temperature on the stagnation pressure has been examined below 4 atm, and an empirical equation is proposed. These results differ from a previous report of Felder and Günthard who reported no conformational cooling in a supersonic jet of this molecule.