基于共振增强多光子电离技术的慢电子速度影像应用
Application of slow electron velocity map imaging based on resonance enhanced multiphoton ionization

利用激光共振增强多光子电离技术，我们既可以观察中性物种激发态的振动结构也可以获得相应正离子的高分辨电子能谱。采用自行研制的双静电透镜系统对Xe原子在258.00nm激光束下的三光子电离过程展开研究，优化得到飞行时间质谱的质量分辨率(m/Δm)达到1300，慢电子速度成像的电子能量分辨率（ΔE/E）为2.4%，阈值电子能量分辨优于1 meV。在该条件下，开展了分子的电子谱研究，研究了苯的激发电子态共振增强双光子电离光谱和振动态选择的苯正离子的慢电子速度成像谱，通过对谱线归属，获得了1B2u激发态的振动序列和苯正离子的振动能级结构信息。
The utilization of resonance enhanced multiphoton ionization（REMPI）spectra allows us not only to investigate the vibrational structure of the intermediate states in neutral species, but also to acquire the high resolution photoelectron spectra. Three-photon ionization process of Xe atom at 258.00nm laser wavelength was investigated by using home-made double electrostatic-lens optics. A mass resolution(m/Δm) of ～1300 for Time of Flight Mass Spectrometer (TOFMS), electron energy resolution (ΔE/E) of 2.4% for Velocity-map imaging (VMI) and the energy resolution near threshold photon <1meV have been achieved. The REMPI spectrum of benzene in the excited state and slow electron velocity-map imaging spectra of benzene in the cation are obtained by the optimum parameters. The vibronic levels of 1B2u excited state and the vibrational structure of benzene cation are assigned unambiguously.