HIGH-RESOLUTION FTIR JET SPECTROSCOPY OF CCL2F2

An experimental system employing a cryopump has been assembled for high-resolution FTIR spectroscopy of species cooled in a supersonic jet expansion. Coupled to a Bruker IFS 120HR interferometer, it involves an external sample chamber and transfer optics allowing 11 optical passes of the infrared beam. Tests with CO and N2O indicate rotational temperatures in the range 6-30 K. By heating the nozzle, significant population of vibrational states can be achieved without sacrificing rotational cooling. The mid-infrared spectrum of Freon-12, CCl2F2, has been recorded and the nu8 C-type band at 1161 cm-1 analysed. Rotational constants for (CCl2F2)-Cl-35 and (CClClF2)-Cl-37-Cl-3 have been calculated and the rotational temperature estimated at 40 K.