Combined interferometric and absorption-spectroscopic technique for determining molecular line strengths: Applications to CO2

A diode-laser-based technique has been developed for absolute line strength measurements with high precision and accuracy, combining a spectroscopic determination of the integrated absorbance with an optical measurement of the absorption path length by means of a Michelson interferometer. This method has been applied to several (CO2)-C-12-O-16 vibrorotational transitions belonging to the nu(1)+2nu(2)(0)+nu(3) combination band, in the spectral region around 2 mum. The 1sigma overall accuracy in line strength determination ranges between 0.4% and 0.7%, while the experimental reproducibility is estimated to be around 0.1%. To our knowledge, these levels are the highest ever reached before. The pressure-broadening coefficients for the same transitions are also reported.