锂原子的光激发和电场电离

Electric Field Ionization of Lithium Atom

对处于25P Rydberg态的锂原子进行了电场电离的理论研究。采用三步共振激发技术,沿2S1/2—2P3/2—3D3/2—25P的激发路径,使锂原子在25P Rydberg态上布居,再施加脉冲电场使其电离。针对上述光激发+场电离过程所涉及的各个原子态的粒子布居,建立起速率方程组,再通过拉普拉斯变换方法推导出各个态的粒子布居率和电离效率的解析表达式,以便对各个阶段的物理机理和特性进行理论分析。通过用Matlab语言自编的计算软件,不但定量分析了不同激光参数对光激发过程的影响,还研究了脉冲电场的参数对原子电离率的影响。研究表明,在本激发路径下,难以显著提高对25P Rydberg态的光激发效率,因而限制了电场电离的总体效率。

Electric field ionization of the Li 25P Rydberg state is studied theoretically with the three-step resonant excitation,2S1/2—2P3/2—3D3/2—25P ,and ionized by an external electric-field pulse. The rate equations for the related particle population of different atomic states are set up for the above process, from which the analytic solutions of the particle populations of different states and ionization efficiency are derived with the Laplace transformation. In order to explore the physical mechanism and characteristics of each step during the process, a home-made Matlab programs is written. The impact of both parameters of laser and electricfield pulses used in photoexcitation and electric-field ionization processes on the ionization probability has been analyzed quantitatively. The study indicates that with the present excitation scheme photoexcitation efficiency of the 25P Rydberg state is hard to be improved significantly, leading to the limitation of overall efficiency of the electric-field ionization.