Laser bandwidth effects in quantitative cavity ring-down spectroscopy

We have investigated the effects of laser bandwidth on quantitative cavity ring-down spectroscopy using the 'R transitions of the b(v = 0) <-- X(v = 0) band of molecular oxygen. It is found that failure to account properly for the laser bandwidth leads to systematic errors in the number densities determined from measured ring-down signals. when the frequency-integrated expression for the ring-down signal is fitted and measured laser line shapes are used, excellent agreement between measured and predicted number densities is found.