The Study Of NO High-excited States

The resonance-enhanced multi-photon ionization(REMPI) spectrum of NO in the region of 420-680nm is obtained by using Optical Parameter Generator and Amplifier (OPG/OPA) as radiation source. The OPG/OPA was pumped by Nd:YAG (Quantel) laser. According to (he theoretical analysis, the peaks on the REMPI spectrum are ascribed to the intermediate resonant state A2Σ+ F2,H2△,C2Σ,D2Л F2Σ,H2△ and E2Σ. This indicates that the ionization progress of NO is REMPI progress via the intermediate states A2Σ+(2+2), F2Σ,H2△, C2Σ,D2Л(3+1 or 3+2), F2Σ,H2△ and E2Σ(4+1). The relationship between ion signal and laser intensity supports above conclusion also. At the same time, the optimum pressure is determined from the ion signalversus pressure. Based on the experiment, the molecule constants about NO resonant intermediate states are calculated. The experimental results show that the transition from NO ground state to the resonant intermediate state follows special selection rule. The main reason for the special selection rule of NO is that the most excited states (including the A2Σ+,F2Σ,H 2△, C2Л,D2Σ,E2Σ) are Ryderberg type and the ground state configuration of NO is sufficiently appreciated by that of an alkali atom. So the selection rule of NO is analogous to that of alkali atom and different from the usual diatom molecule. The conclusion is further affirmed by the two photon fluorescence excitation spectrum of NO.