High-sensitivity spectroscopy of CO2 around 4.25 mu m with difference-frequency radiation

We demonstrate the possibility to perform very high-sensitivity spectroscopy Of CO2 around 4.25 mum wavelength, by use of a difference-frequency radiation source and a White-type multipass absorption cell. Several methods for fringing noise reduction were successfully adopted. In particular, a novel technique to reduce fringes by choosing proper values of the frequency modulation amplitude is described in detail. Pressure-broadening measurements of high-J rovibrational transitions are presented. Achievable laboratory and field sensitivity limits are discussed. (C) 2002 Elsevier Science