NO(3+1)共振增强的多光子离化谱

The Resonance-Enhanced Ionization Spectrum of NO via(3+1) Multiphoton Process

用皮秒脉冲高功率Nd∶YAG激光器抽运的光学参量发生/放大器作激发源,获得了NO分子在420-500 nm波长范围内的多光子离化谱,光谱图呈现分离谱的特征,表明在该波长区间NO分子以多光子共振方式离化。离化信号随激光强度的近四次方变化关系表明,在420-500 nm波长范围内NO分子吸收4个光子而离化。通过对谱线的标识,首次分离出NO分子以E^2Σ激发电子态为中间共振态的（3＋1）多光子离化光谱序列,由谱线序列峰值波长得到NO分子E^2Σ电子态的振动常数,从而实现了采用多光子离化技术对该态能级结构的实验研究。

The resonance-enhanced multi-photon ionization （REMPI） spectrum of NO in the region of 420-500 nm was obtained with the optical parameter generator and amplifier pumped by a Nd ： YAG laser as the radiation source. The spectrum presents the characteristic of banded structure. This indicates that NO molecule is ionized in a resonant manner and via a multi-photon process in this wavelength region. The fact that the variation of the ion signal intensity versus the laser intensity is near quartic suggests that the NO molecule is ionized by a four-photon process. Based on the theoretical calculation, a spectral progression that comes from the （3 ＋1） multiphoton process and via E ^2Σ, intermediate resonant state is ascribed. The ionization pathway of NO molecule can be expressed as NO（X^2 Π） →3hv NO（E ^2Σ） →hv NO^＋ ＋e. The vibration constants of NO E^2Σ state were obtained from analyzing the result. So the study of the energy level structure of NO E^2Σ state by the technique of REMPI was realized for the first time.