Abstract：NO is an important pollutant molecule，and plays a key role in generatinｇ photochemical smog and destroying O3 in the atmosphere. So researchers have always been interested in it. In our experiment, the optical parameter generator and amplifier (EKSPLA) pumped by Nd:YAG (Quantel) laser were used as the radiation source. The REMPI spectrｕm of NO in the region of 460-570 nm was obtained. Based on theoretical calculation, most of the lines were attributed to the Ｘ2Π→D2Σ transition. The ionization pathway was discussed in detail, which can be shown as NO(Ｘ2Π)3hνNO(D2Σ)2hνNO＋＋e. The vibration fundamental and force constant of NO(D2Σ) state were calculated. The results are ωe＝2 339.2 cm-1 and k=2.41×105 dｙn·cm-1. For fｕtｕre worｋ, the resolution of the radiation source will be improved in order to obtain more information of the D2Σ state.
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