（1＋1）多光子电离几率的理论研究  

Theoretical Analysis of Ionization Probability about 1 ＋ 1 Multiphoton Ionization Process

作　　者：张贵银[1] 靳一东[1] 

机构地区：[1]华北电力大学数理学院,河北保定071003

出　　处：《光学学报》2013年第F06期258-261,共4页Acta Optica Sinica

基　　金：国家自然科学基金（11174078）资助课题.

摘　　要：通过求解光和物质相互作用的速率方程，获得了（1＋1）共振增强多光子电离过程中电离几率的解析表达式，以该表达式为基础，理论模拟了激光强度、激光脉宽、碰撞弛豫速率等参量对（1＋1）多光子电离几率的影响。发现电离几率随激光强度、激光脉宽的增加而增大，到一定程度达到饱和，激光脉宽越大，电离几率随激光强度增加的速率越快，饱和光强值越小。当光强超过饱和值时，电离几率随激光强度的增加围绕饱和值1振荡，电离几率出现大于1的情况，这一有悖于事实的理论结果表明，由于强激光场和物质的相互作用改变了物质系统的能级结构特征，描述光与物质相互作用的速率方程理论不再适用。理论结果还显示，电离几率随碰撞弛豫速率的增加呈线性规律减小，但变化很小，所以样品气压对多光子电离几率的影响可忽略。The analytic formula of the ionization probability in the process of （1 ＋1 ） resonance enhanced multiphoton ionization （REMPI） is derived from the dynamic rate equation about the interaction of photon and material. Based on this formula, the influence of laser intensity, laser pulse duration and collision relaxation rate on the ionization probability is numerically simulated. It is shown that the ionization probability increases with laser intensity and laser pulse duration, and gets to saturation to some extent. The higher of the laser pulse duration, the faster of the ionization probability increase with laser intensity. The saturation laser intensity is lower also. The ionization probability will vibrate around the maximum value 1 when laser intensity is larger than the saturation value. The fact that the ionization probability is larger than 1 indicates the theory of rate equation is not suitable as the result that the interaction of the strong laser field with matter will change the character of energy levels. The results also show that the ionization probability will decrease in linear manner with the increase of collision relaxation rate, but the variation is very small. So the effect of air pressure on multiphoton ionization probability can be ignored.

关 键 词：非线性光学 多光子电离几率 激光特性 碰撞弛豫速率 

分 类 号：O433.2[机械工程—光学工程]