Two-photon polarization spectroscopy and (2+3)-photon laser induced fluorescence of N-2

Two-photon induced polarization spectroscopy (TIPS) for the detection of molecular nitrogen is demonstrated. Laser induced fluorescence (LIF) from N⁺₂, which was created via a (2 + 3)-photon resonance from N₂, was monitored simultaneously to allow a quantitative comparison between the two techniques in different operating regimes. Power dependence checks for both techniques were performed and the effects of collisional partners were investigated in different gas flow mixtures. These preliminary results suggest that TIPS is not as severely affected by molecular quenching collisions as LIF. The high signal levels obtained prove that the technique is sensitive and may have potential as diagnostic tool for combustive and non combustive flows.