【作者】 郭晶；

【导师】 杨玉军；

【作者基本信息】 吉林大学 ， 原子与分子物理， 2018， 硕士

【摘要】 超短强激光与原子分子相互作用可以观察到许多非线性现象如高次谐波、高阶阈上电离,挫败隧穿电离等。利用激发态原子可以实现对中性原子加速,因而激发过程的研究最近成为人们研究的重点。本文通过数值求解三维含时薛定谔方程,计算了原子在超强超短激光脉冲作用下的激发。首先系统地研究了在线偏振激光条件下,激发态几率及其在各个主量子数和角量子数上的分布。发现原子激发的几率随着入射激光强度的增加呈现“knee”结构。通过分析激发几率在主量子数上的布居发现该结构产生来源是基态和激光电场缀饰高激发态之间的共振跃迁。随着入射激光强度的增加,原子的激发几率在不同角量子数上的分布呈现出奇偶相间的规律。这一结果表明原子的激发过程除了要满足能量共振的条件,还需要满足角动量守恒。在此基础上,分析了偏振效应对原子激发过程的影响。发现在相同入射激光能量下,随着入射激光椭偏率的增加,原子的激发几率逐渐减小,几率分布在更高主量子数n的几率逐渐增加。和波长为400nm驱动激光相比,波长为800nm的激光脉冲的激发几率的随偏振增加下降速率更大。更多还原

【Abstract】 Many nonlinear phenomena can be observed when ultrashort intense laser pulses interact with atoms and molecules,for example,high-order harmonic,high-order above threshold ionization ionization,thwarted tunneling ionization,etc.Neutral atom acceleration can be achieved by using excited atom,therefore,the study of excitation process has recently become the focus of research.In this paper,the excitation of atoms under ultrashort intense laser pulses is calculated by solving the threedimensional time-dependent Schrodinger equation numerically.First of all,the probability of excited states and its distribution on the principal quantum number and angular quantum number are studied systematically under the condition of on-line polarization laser pulses.We find that the excitation probability of the atom exhibits a “knee” structure with the increase of the intensity of the incident laser pulse.By analyzing the distribution of the excitation probability on the principal quantum number,it is found that the source of the structure is the resonant transition between the ground state and the highly excited state of the laser electric field.The distribution of atomic excitation probability in different angular quantum numbers shows the law of even and odd phase with the increase of incident laser pulse intensity.The results show that the excitation process of atoms not only satisfies the condition of energy resonance,but also satisfies the conservation of angular momentum.On this basis,we analyze the effect of polarization on the atomic excitation process.We find that the excitation probability of atoms decreases with the increase of the degree of polarization of the laser pulses at the same laser pulses energy,the excitation probability is distributed on the higher principal quantum number,and the excitation probability increases gradually.The excitation probability of laser pulse with wavelength of 800 nm increases with the increase of polarization,which is higher than that of 400 nm laser pulse at wavelength.更多还原