Cooling molecules in a cell for FTMW spectroscopy

Gas phase benzonitrile, acetone, 1-2 propanediol, fluorobenzene, and anisole molecules are produced in a cell at a temperature of 8 K, and detected via Fourier transform microwave spectroscopy (FTMW). Helium buffer gas is used to cool the molecules originating from a high flux room temperature beam. This general, continuous source of cold molecules offers comparable spectral resolution to existing seeded pulsed supersonic beam/FTMW spectroscopy experiments but with higher number sensitivity. It is also an attractive tool for quantitative studies of cold molecule-helium and molecule-molecule elastic and inelastic collisions. Preliminary data on helium-molecule low temperature rotational and vibrational relaxation cross-sections are presented. Applications of the technique as a sensitive broad spectrum mixture analyser and a high resolution slow-beam spectrometer are discussed.