Broadband cavity ringdown spectroscopy of the NO₃ radical

Cavity ringdown spectroscopy (CRDS) has been demonstrated using a broadband (20 nm) laser source and a two-dimensional clocked detector array. Absorption spectra of dilute samples (50-500 parts per trillion) of the nitrate radical, NO₃, have been obtained between 650 and 670 nm by monitoring simultaneously the time and wavelength resolved output of a ringdown cavity. The potential of broadband CRDS for making measurements on samples containing multiple absorbers (e.g., atmospheric samples) is shown by applying analysis methods from differential optical absorption spectroscopy to quantify the NO₃ concentration in the presence of nitrogen dioxide impurities.