[Laser fluorescence excited spectrum of NO via alpha2sigma<--chi2pi transition]

Two-photon fluorescence excited spectrum of NO induced by Nd: YAG laser pumped optical parameter generator/amplifier as excitation source was obtained in the range of 420-472 nm. With this technique, the structure of the energy levels of NO molecule in alpha2sigma electronic state was investigated. The peaks of the spectrum were attributed to alpha2sigma(v' = 0,1)<--chi2pi(v" = 0) transition. The near square dependence of fluorescence signal on the laser intensity indicates a two-photon process. The ground-vibrational-state oscillation frequency and the force constant of alpha2sigma state were calculated. The fluorescence lifetime of alpha2sigma(v' = 0) state under the pressure of 266 Pa was also obtained by measuring fluorescence decay curve of alpha2sigma(v' = 0) states. It is about 53.76 ns. Fitting the curve of the fluorescence radiant lifetime versus pressure, the spontaneous radiant lifetimes and the rate coefficient of nonradiative transition relaxation of alpha2sigma(v' = 0,1) states were deduced.