[Mechanism of resonance-enhanced multiphoton ionization of NO molecule].

NO molecule is a diatomic molecule with different nucleus. It is a serious pollutant and is harmful to the health of the generation. It comes mainly from inflammation process using coal as burning material. So researchers have always been interested in it. The Resonance-Enhanced Multi-Photon Ionization (REMPI) spectrum of NO has been obtained in the range of 420-480 nm with a Nd:YAG laser pumped optical parametric generator and amplifier as the radiation source. The ionization pathway of NO molecule was acquired with the assignment of the spectral lines. NO molecules are ionized via the resonant intermediate state A2 sigma+ and by a (2 + 2) REMPI process. On the basis of theoretical rate equation and with the condition that the duration of the laser pulse is very short (approximately 35ps), the dependence of ion signals on laser intensity was deduced. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with the experimental result.