Absorption spectroscopy of N(2)O with phase-diffusion-noise sidebands on a lead-salt tunable diode laser.

The broad phase-diffusion-noise spectrum of a lead-salt tunable diode laser (TDL) has been exploited for the detection of absorbances produced from low-pressure N(2)O vapor in the 4.47-µm spectral region. This effect has previously been observed in the detection of electronic transitions in rubidium, cesium, and molecular oxygen with anAlGaAs TDL operating in the 0.700-0.800-µm region. For the first time to our knowledge, this paper presents evidence of this phenomenon when a midinfrared rovibrational absorption line is monitored. The technique is also compared with traditional TDL spectroscopic methods for its applicability to trace-vapor monitoring.