Diode laser overtone spectroscopy of CO2 at 780Â nm

Overtone absorption lines of 12C16O2 have been examined by using a tunable diode laser (TDL) spectrometer in the region around 12770cm-1. The spectrometer sources are commercially available double heterostructure InGaAlAs TDLs operating in the “free-running” mode, which allowed the detection of the line positions within 0.01cm-1. The observed carbon dioxide absorption lines belong to the ν1+5ν3 ro-vibrational band with rotational quantum number J up to 48. The minimum absorbance detected by the spectrometer (≃5×10-6) permitted to observe the weakest lines having the absorption cross section of the order of ≃1×10-27cm2/molecule.