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.