High-resolution cavity ring-down absorption spectroscopy of nitrous oxide and chloroform using a near-infrared cw diode laser

A high-resolution cavity ring-down spectrometer has been constructed employing a tuneable cw diode lasing around 1300 nm (bandwidth and frequency stability better than 1 MHz) and a frequency-matched cavity. The performance of the spectrometer has been tested on the Σ–Σ combination band ν1+3ν3 of 14N216O around 7780 cm−1 at Doppler-limited resolution, for which we report integrated absorption cross-sections, line positions and detection limits. CH-chromophore absorptions of 12CHCl3 between 7700 and 7750 cm−1 have also been observed, in agreement with previous predictions with an effective Hamiltonian based on a Fermi-resonance polyad model.