Optical-optical double resonance LIF detection of N2 (A3Σu+) in high pressure gas discharges

An optical-optical double resonance (OODR) laser induced fluorescence (LIF) for the detection of the N2 (A3Σu+) metastable is described. OODR employs the double laser excitation of A-B and B-C nitrogen transitions. Here it is proposed as a sensitive approach to detect N2 (A3Σu+) in high-pressure discharges. We have tested its sensitivity with respect to conventional single photon LIF by an excitation/detection scheme in which the two wavelengths required are generated by a provisional single laser setup. Other single laser configurations that might allow a sensitivity close to two orders of magnitude larger than that of conventional LIF are proposed. Such gain can be particularly useful for the detection of N2 (A3Σu+) in non-equilibrium, high-pressure discharges