We present preliminary results of resonant (2 + 2) multiphoton ionization of NO in flames near 452 nm. Temperature profiles are obtained from Boltzmann analysis and from spectral simulations of the resonance-enhanced multiphoton ionization (REMPI) rotational spectra of the NO A2∑÷←X2∏ (0,0) band. Interest in this work was encouraged by previous REMPI flame studies of NO1,2, as well as by possible problems that may be encountered in NO2 flames using laser λ < 405 nm which may perturb the probe volume by photolysis of NO2 (readily photolyzed at λ < 405 nm).3 Clearly, LIF of NO around 220 nm, O-atom LIF near 226 nm4, and OH LIF flame thermometry near 300 nm may be affected by NO2 photolysis. Therefore, development of a method for NO detection as well as for flame thermometry requiring laser λ > 405 nm would be very desirable.
© 1991 Optical Society of AmericaPDF Article