Temperature- and species-dependent quenching of NO A 2∑ + (v′ =0) probed by two-photon laser-induced fluorescence using a picosecond laser
Journal of Chemical Physics
We report improved measurements of the temperature-dependent cross sections for the quenching of fluorescence from the A +2 (v′ =0) state of NO. Cross sections were measured for gas temperatures ranging from 294 to 1300 K for quenching by NO (X Π2), H2 O, CO2, O2, CO, N2, and C2 H2. The A +2 (v′ =0) state was populated via two-photon excitation with a picosecond laser at 454 nm, and the decay rate of the fluorescence originating from A +2 (v′ =0) was measured directly. Thermally averaged quenching cross sections were determined from the dependence of the fluorescence decay rate on the quencher gas pressure. Our measurements are compared to previous measurements and models of the quenching cross sections, and new empirical fits to the data are presented. Our new cross-section data enable predictions in excellent agreement with prior measurements of the fluorescence lifetime in an atmospheric-pressure methane-air diffusion flame. The agreement resolves discrepancies between the lifetime measurements and predictions based on the previous quenching models, primarily through improved models for the quenching by H2 O, CO2, and O2 at temperatures less than 1300 K. © 2006 American Institute of Physics.