强激光场中的原子电离

按照激光场的强度，原子与强激光场的相互作用可以大致分成几个典型区域，文章概述了不同区域内民离的基本特征和相应的理论模型，重点介绍了描述强场电离程的准静态理论，并讨论了各种理论的适用范围。     

惰性气体原子和离子在强激光场中的隧道电离

在隧道电离区域利用ADK模型并考虑了激光的体积效应,对惰性气体原子及各价离子在强激光场中的电离产额进行了计算,并与BSI模型及实验结果进行了比较,结果发现ADK模型的结果会随着原子序数的增加而变好,尤其对Xe离子,不需要进行强度转换就能给出很好的结果．由此可以得出结论：对于重原子（或离子）,用ADK模型得到的离子产额与实验结果符合得更好．最后通过分析ADK模型的适用范围,给出了和计算结果相一致的结论．     

强激光场中长程势与短程势原子产生高次谐波与电离特性研究

用数值方法求解含时薛定谔方程，研究了具有长程势和短程势的一维原子在强激光场中的高次谐波和电离特性. 在强激光场中，长程势和短程势原子产生的高次谐波具有相似的特性，对应的平台和截止位置相同，但是短程势原子没有低阶的高次谐波，而长程势和短程势原子在激光场中的电离概率明显不同. 研究结果表明，原子的激发态结构对低阶的高次谐波和原子的电离概率有重要影响. 关键词： 强激光场 高次谐波 电离概率     

光强、频率对强激光场中的多原子分子离子增强电离行为的影响

通过利用短时指数传播子的对称分割和快速傅里叶变换,数值求解一维含时薛定谔方程,研究了一维多原子分子离子在超强脉冲强激光场中的增强电离(EI)行为,给出了激光强度和频率对增强电离的影响.计算表明随着激光频率的增加,增强电离的临界键长变小,电离概率 也减小;随着激光强度的增加,电离概率增加,当强度增加到一定值时,就不再出现增强电离现象. 关键词： 强激光场 分子离子 增强电离     

高阶离化对强激光场诱导自电离的影响

本文讨论了以往强激光诱导自电离理论所忽略的二阶以上的高阶离化效应,得到了自电离谱的解析表达式,详细研究了高阶离化的影响。结果表明,当激光场足够强时,高阶离化使自电离谱和自电离态的缀饰态产生显著变化。 关键词：     

强激光场中模型氢原子和真实氢原子的高次谐波与电离特性研究

利用数值方法求解含时薛定谔方程，研究了一维、二维模型氢原子和真实的三维氢原子在强激光场中产生的高次谐波和电离特性.结果表明，在多光子电离区域和过垒电离区域，模型氢原子与真实的氢原子产生的高次谐波和电离概率差别很小；在隧道电离区域，它们产生的高次谐波的平台特征和截止位置相似，电离概率随时间变化的趋势相近，但其数值有明显的差异.对产生这种差异的原因进行了分析. 关键词： 强激光场 高次谐波 电离概率     

强激光场中氢负离子双光子电离能量谱的研究

利用强场近似（Strong field approximation,SFA）方法研究氢负离子（H ）在强激光场中双光子电离的能量谱,所得到的电离谱随角度的变化规律与实验结果符合得很好.进一步的研究表明, H 离子在强激光场中双光子电离的能量谱与有质动力能有关.激光场强度越大,光电子的有质动力能也越大,能量谱向左移动越明显.我们的结果表明,使用强场近似是一种研究负离子在强激光场中电离过程的有效方法.     

强激光场中氢负离子双光子电离能量谱的研究

利用强场近似(Strong field approximation,SFA)方法研究氢负离子(H-)在强激光场中双光子电离的能量谱,所得到的电离谱随角度的变化规律与实验结果符合得很好.进一步的研究表明,H-离子在强激光场中双光子电离的能量谱与有质动力能有关.激光场强度越大,光电子的有质动力能也越大,能量谱向左移动越明显...     

强激光场中一维原子的渐近边界条件

用Fourier变换推导了强激光场中一维原子模型的渐近边界条件,分析了三类渐近边界条件的误差,用第一类渐近边界条件和非齐线性正则方程的辛算法计算了强激光场中一维氢原子的几率分布和平均能量,并将结果与理论分析进行了比较.     

激光场中类氢原子的电离本征值

光场下类氢原子的Schrdinger方程可用缀饰势方法求解.波动方程展开为Floquet分波后,可以得到弱光场或强光场下近似的径向波函数和复的电离本征值,然后计算了共振能量和半宽度.     

Influence of the laser field polarization on the electron impact ionization of hydrogen

The triple differential cross-sections for the ionization of hydrogen by electron impact in the presence of a laser field have been calculated in the coplanar asymmetric geometry by using the first Born approximation and the symmetric geometry by using the Coulomb-Born approximation at an incident electron energy of 250 eV. The variation of the triple differential cross-sections, for fixed values of the angles of scattering and ejection, is studied as a function of the linear polarization of the laser field. The changes are quite amenable to experimental investigation.     

Multiphoton and tunneling ionization of atoms in an intense laser field

We study the ionization probabilities of atoms by a short laser pulse with three different theoretical methods,i.e.,the numerical solution of the time-dependent Schro¨dinger equation(TDSE),the Perelomov-Popov-Terent’ev(PPT) theory,and the Ammosov-Delone-Krainov(ADK) theory.Our results show that laser intensity dependent ionization probabilities of several atoms(i.e.,H,He,and Ne) obtained from the PPT theory accord quite well with the TDSE results both in the multiphoton and tunneling ionization regimes,while the ADK results fit well to the TDSE data only in the tunneling ionization regime.Our calculations also show that laser intensity dependent ionization probabilities of a H atom at three different laser wavelengths of 600 nm,800 nm,and 1200 nm obtained from the PPT theory are also in good agreement with those from the TDSE,while the ADK theory fails to give the wavelength dependence of ionization probability.Only when the laser wavelength is long enough,will the results of ADK be close to those of TDSE.     

氢原子在红外激光和极紫外脉冲组合场中的阈上电离

通过求解氢原子在强红外(IR)激光和极紫外（XUV）脉冲组合场中的三维含时薛定谔方程(TDSE),理论研究了XUV脉冲的加入对光电子能谱和二维光电子动量分布的影响.计算结果表明,与仅由红外场驱动的情况相比,组合场驱动下的光电子能谱和二维光电子动量分布中呈现出明显的干涉增强结构,干涉结构对XUV脉冲的强度、光子能量和时间延迟都有很强的依赖,该方案可实现高能阈上电离谱的选择性增强.     

用伪谱方法计算强激光场中一维原子的阈上电离谱

引入非线性空间变换,用伪谱方法求解了一维原子在强激光场中的薛定谔方程,再利用B样条函数和傅立叶级数的线性组合构造原子未微扰的本征函数,计算了一维原子在强激光场中的阈上电离谱,其结果与分裂算符法得到的结果符合得很好.     

Entangled trajectories during ionization of an H atom driven by n-cycle laser pulse

We study the ionization of an H atom in a linearly polarized laser field with different optical cycle numbers by calculating the entangled trajectories in phase space. The results indicate that, for a two-cycle laser pulse, the entangled trajectory is simple owing to the simple laser electric distribution. As the number of optical cycles increases, the complexity of the laser electric field distribution, and subsequently, that of the entangled trajectories increase. From these entangled trajectories, re-scattering ionization can be observed. Further, we investigate the effect of quantum force on trajectories by comparing them with classical trajectories. We find that for few-cycle laser pulses ($n_p=2$ and 4), the effect of the quantum force is more distinct than classical behavior, whereas for longer laser pulses ($n_p=6$ and 8), it is quite similar to the classical behavior. Because of the quantum force, the final kinetic energy is slightly higher than that obtained by classical calculation. The different initial positions have some influence on the individual trajectories, but the individual trajectories still keep similar configuration to the mean trajectories.     

重力场中原子的衍射态及其概率分布

使用量子力学中Feynman的路径积分方法,导出了重力场中原子经单缝、双缝及多缝衍射后的量子态及其概率分布.在一定近似条件下,证明了干涉条纹的移动与重力加速度有关,而条纹间隔与重力加速度无关.     

Influence of the virtual photon field on the squeezing properties of atom laser

This paper investigates the squeezing properties of an atom laser without rotating-wave approximation in the system of a binomial states field interacting with a two-level atomic Bose--Einstein condensate. It discusses the influences of atomic eigenfrequency, the interaction intensity between the optical field and atoms,parameter of the binomial states field and virtual photon field on the squeezing properties. The results show that two quadrature components of an atom laser can be squeezed periodically. The duration and the degree of squeezing an atom laser have something to do with the atomic eigenfrequency and the parameter of the binomial states field, respectively. The collapse and revival frequency of atom laser fluctuation depends on the interaction intensity between the optical field and atoms. The effect of the virtual photon field deepens the depth of squeezing an atom laser.