NO分子H^2∑^+态共振增强多光子离化谱

Resonance-enhanced Multiphoton Ionization Spectrum of NO by H^2∑ State

利用皮秒Nd:YAG激光器三倍频(355nm)输出泵浦的光学参量发生/放大器作激发源,获得了NO分子在585～645nm波长范围内的共振增强多光子离化(REMPI)谱。离化信号随激光强度的近5次方变化关系表明,NO分子吸收5个光子而离化,根据计算可以确定在此波长范围内NO分子通过中间共振态H2∑态而离化,离化通道为NO(X2∏)4hνNO(H2∑)1hνNO++e。由实验数据计算了H2∑态的基振动频率和振动力常数,并讨论了NO分子在4+1离化过程中所表现出的特殊跃迁选择定则。

Resonance-enhanced multiphoton ionization(REMPI) spectrum of NO in the region of 585～645 nm was gained by using optical parameter generator and amplifier (OPG/OPA) as radiation source.The OPG/OPA was pumped by picosecond Nd:YAG laser.The variation of the ionization signal versus laser intensity is near quintic.This indicates that NO molecule ionized by absorbing five photons.Calculation makes out that NO molecule is ionized though intermediate resonant state H^2∑.Ionization pathway can be shown as:NO(X^2∏) 4 hνNO(H^2∑) 1 hνNO^++e.The vibration fundamental and force constant about NO H^2∑ state were calculated.The results are ω_e=2 371 cm^(-1) and k=2 476 N·cm^(-1).Special selection rules of NO molecule in the 4+1 ionization process were also discussed.