A NOVEL CRYOGENIC MOLECULAR-BEAM - APPLICATION TO SUPERSONIC JET SPECTROSCOPY OF GASES

A novel method for molecular supersonic free-jet spectroscopy, which uses a cryopump rather than mechanical pumps to maintain a low background pressure, is described. Advantages of this method include its low cost, relative ease of installation in many types of spectrometer and the potential for efficient recovery of valuable samples. The technique has been demonstrated with a compact liquid-nitrogen cryopump installed in the sample compartment of an FTIR spectrometer. Jet-cooled infrared rovibrational spectra Of CO2, NO2 and N2O4 indicate a similar degree of rotational and vibrational cooling as that obtained using conventional mechanical pumps.