Sequential two-photon-laser-induced fluorescence: a new method for detecting atmospheric trace levels of NO

Earlier approaches used for the detection of NO under atmospheric conditions of composition and pressure have involved single-photon excitation of NO with the monitoring of fluorescence at wavelengths which are red shifted relative to the excitation wavelength. Attention is given to a sequential two-photon-laser-induced fluorescence (TP-LIF) technique which has potentially far greater sensitivity than the single-photon method because the resulting fluorescence is blue shifted relative to the shortest laser wavelength used to pump NO optically. It now appears that the sequential TP-LIF technique has the potential for detecting atmospheric NO levels as much as a factor of 25 times lower than that possible by using the single-photon method.