A sharp wavelength dependence on the amount of incident laser energy necessary to ignite a premixed flow of H2/O2 at atmospheric pressure is reported. This wavelength dependence exhibits a spectral profile similar to the two-photon fluorescence excitation curve for flame oxygen atoms, and the respective peaks correspond to exactly the same wavelength near 225.6 nm. This similarity clearly indicates that oxygen-atom production and subsequent excitation is an important step in the efficient (∼0.5-mJ) laser ignition of H2/O2 flows in this wavelength region. In addition, the dependence of the incident laser energy on the equivalence ratio reveals that the most efficient ignition occurs far into the fuel-lean region. This behavior further underscores the importance of the interaction between the UV laser and the oxidizer (O2) component in the ignition of this reactive mixture.
© 1986 Optical Society of America
Brad E. Forch and Andrzej W. Miziolek, "Oxygen-atom two-photon resonance effects in multiphoton photochemical ignition of premixed H2/O2 flows," Opt. Lett. 11, 129-131 (1986)