本文分析了在XeCl准分子激光作用下NH_3分子的多光子电离质谱形成机理。所建立的动力学模型包括主要由经过中间态(6)和(1)的(2+1)共振多光子电离,生成NH_3~+;离子-分子反应形成大量的NH_4~+;经(6)态的(2+2)共振多光子电离,可能产生低产额的NH_2~+。这个模型的速率方程解与实验测量符合得很好,并在离子流强度对激光脉冲宽度的依赖关系中预示直接电离或间接电离机制的信息。

This paper analyses the formation mechanism in NH3 multiphoton ionization mass spectra induced by an XeCl excimer laser. Established model includes that NH3+ are mainly yielded in (2+1) multiphoton. ionization via the Eydberg states B(6) and C (1), and NE4+ formed from ion-molecule reaction, NH3+(NH3, NH2)NH4+ and very low-yield NH2+ most probably produced from (2 + 2) multiphoton ionization via resonant intermediate state B(6). The rate equation solution for this model is in good greement with our experimental results. It predicts that the information oil direct or Indirect ionization mechanisms are involed in the dependences of ion intensity on laser pulse duration.