激发光线宽对原子光致漂移速率的影响  

Influence of laser linewidth on light-induced drift velocity of atom

作　　者：杨佳琦 刘加东 刘涛[2] 张志忠[2] Yang Jia-Qi;Liu Jia-Dong;Liu Tao;Zhang Zhi-Zhong(Department of Engineering Physics, TSinghua University, Beijing 100084, China;Research Institute of Physical and Chemical Engineering of Nuclear Industry, Tianjin 300180, China)

机构地区：[1]清华大学工程物理系,北京100084 [2]核工业理化工程研究院,天津300180

出　　处：《物理学报》2018年第11期99-105,共7页Acta Physica Sinica

摘　　要：在光致漂移效应的研究中,激发光线宽会改变原子激发的速度选择性,进而影响漂移速率的大小.本文以原子光致漂移速率方程理论为基础,利用强碰撞模型描述原子与缓冲气体的碰撞作用,运用数值方法对速率方程进行求解计算,研究了激发光线宽对原子漂移速率的影响.研究结果表明,其他条件相同时,随着线宽的增大,漂移速率的值呈现先增大后减小的趋势.存在一个最佳的激发光线宽,使得原子的漂移速率达到最大值.最佳线宽与激发光功率密度、温度和缓冲气体压强有关.为了获得最佳的光致漂移效果,激发光应工作在最佳线宽条件下.当激发光线宽在最佳线宽附近波动时,设置激发光线宽略大于最佳线宽可减少线宽波动对漂移速率的影响,对获得较大漂移速率更为有利.Light-induced drift has many applications in astrophysics, semiconductor physics, and isotope separation. Lightinduced drift velocity is a key parameter to characterize the effect of light-induced drift. Laser linewidth exerts a great influence on light-induced drift velocity through influencing the velocity selectivity of atomic excitation, so it is an important factor that cannot be ignored in the study of light-induced drift. However, in existing theoretical studies, the influence of laser linewidth is seldom considered and the exciting light is always treated as monochromatic light. Furthermore, in a few theoretical studies about laser linewidth, the numerical model adopted does not include all the factors of light-induced drift, such as energy level degeneracy, hyperfine structure, and collision model, which will cause the error of calculation. In order to study the influence of laser linewidth on light-induced drift velocity, a four-level rate equation model is established to describe the atomic energy level transition in the process of light-induced drift. In the theoretical model, we introduce strong collision model to describe collisions between atoms and buffer gas. The influences of energy level degeneracy and hyperfine structure are also taken into account. Numerical method is used to calculate the four-level rate equation. According to the calculation results, the influence of laser linewidth on drift velocity of alkali metal atoms is analyzed. The results show that as the linewidth increases, the value of drift velocity first increases and then decreases. There is an optimal linewidth that maximizes the drift velocity. For the best light-induced drift effect, the laser should work under the optimal linewidth condition. When the laser linewidth fluctuates near the optimum linewidth, the laser linewidth should be set to be slightly wider than the optimal linewidth. This can reduce the influence of fluctuation and obtain a better drift effect. In addition, as the laser linewidth increases, the optimum

关 键 词：光致漂移 漂移速率 激光线宽 

分 类 号：O562[理学—原子与分子物理]