Quenching-Free Detection of Nitric Oxide via Time-Resolved Parametric Four-Wave Mixing

摘要

Fluorescence detection is commonly used for quantification of species concentration in combusting environments. Fluorescence yields, however, are extremely susceptible to local environmental conditions, with quenching rates dependent on temperature and number densities of other reactants, intermediates, and products present in the combustion medium. Here, we report the quenching-free detection of gas-phase nitric oxide via a femtosecond time-resolved parametric four-wave mixing optical probe scheme. This approach, which exploits species-specific excitation of a two-photon resonant electronic transition, allows observation of nitric oxide on ultrafast timescales, with signals that are independent of collisions with strongly quenching species.