类氧铥离子辐射跃迁几率和激发态寿命的GRASP计算

使用扩展的相对论多组态自洽场方法计算了类氧铥离子的精细结构能级，跃迁波长，自发辐射跃迁几率，受激辐射跃迁几率，振子强度和激发态寿命。从计算结果发现：在３ｐ－３ｓ跃迁中有４个跃迁很有可能实现粒子数反转而辐射激光。     

钙、锶、钡和汞离子激光中的共振辐射俘获效应

根据Holstein的共振辐射俘获理论，讨论了气体温度和辐射俘获下能级粒子数密度对辐射俘获上能级有效辐射寿命的影响，显示辐射俘获下能级粒子数密度是辐射俘获效应中的主导因素.计算了钙，锶，钡和汞四种离子七条共振-亚稳能级跃迁激光在不同电离率下产生共振辐射俘获效应的阈值条件，发现当电离率为5%时这类激光的出光温度与共振辐射俘获的阈值温度相一致，这与实验得出的电离率为3%—5%相符合.表明达到共振辐射俘获阈值条件是该类激光实现粒子数反转的重要因素.     

原子核与激光的相互作用(一)——激光引起的同质异能态衰变和γLaser

用参量化的方法推导了激光引起的原子核同质异能态共振跃迁的几率,并考虑了激光频率宽度的效应.进而研究了基于以下概念发展γ激光器的可能性:即用强的可见光激光将长寿命的同质异能素转换到能量上近似兼并的短寿命同质异能素,并使后者达到粒子数反转.在分析了同质异能态的粒子占有数随时间变化的基础上,数值计算了这一途径所需要的激光强度.     

原子核与激光的相互作用(一)——激光引起的同质异能态衰变和γ Laser

用参量化的方法推导了激光引起的原子核同质异能态共振跃迁的几率,并考虑了激光频率宽度的效应.进而研究了基于以下概念发展γ激光器的可能性:即用强的可见光激光将长寿命的同质异能素转换到能量上近似兼并的短寿命同质异能素,并使后者达到粒子数反转.在分析了同质异能态的粒子占有数随时间变化的基础上,数值计算了这一途径所需要的激光强度.     

类氧Pr^5^1^＋离子辐射跃迁几率和辐射寿命的GRASP计算

根据扩展的相对论多组态Ｄｉｒａｃ—Ｆｏｃｋ方法，使用我们新近开发的“多功能相对论原子结构程序（ＧＲＡＳＰ）”计算了类氧Ｐｒ５１＋离子的精细结构能级、跃迁波长、自发辐射跃迁几率、受激辐射跃迁几率、振子强度和辐射寿命。从计算结果中发现：在３ｐ－３ｓ跃迁中有１６个跃迁的上、下能级间很有可能实现粒子数反转而辐射激光。这个结果与Ｅｌｔｏｎ［１］的预言进行了比较。     

碱土金属原子激光的共振辐射俘获效应

根据Holstein理论研究了碱土金属原子激光中的共振辐射俘获效应，分别计算了Ca，Sr和Ba蒸气激光在不同半径时产生共振辐射俘获效应的阈值温度、基态粒子数密度和共振能级的有效寿命.发现计算得到的阈值温度与实验报道的开始产生激光的工作温度一致，表明共振辐射俘获效应是这类激光形成粒子数反转的一个重要机制. 关键词： 共振辐射俘获 碱土金属原子激光 阈值温度     

NaS分子4~2Ⅱ→3~2∑~＋跃迁光辐射特性的理论研究

应用＂反射方法＂计算了ＮａＳ分子４２Ⅱ→３２∑＋跃迁几率密度的分布，对其相应跃迁的自发辐射、粒子数反转、受激辐射等问题进行了理论上的探讨．     

Sn激光共振电离质谱分析中电离通道理论探讨

Sn激光共振电离质谱同位素分析中电离通道的选择非常关键。采用Dirac–Hartree–Fock（MCDHF）方法和相对论组态相互作用的GraspVU原子结构计算程序,计算了Sn、Te原子的低激发态能级结构、光谱跃迁几率。通过对Sn质谱分析用灯丝样品进行热蒸发实验,确定了Sn原子在蒸发条件下基态能级粒子布局。结合理论计算跃迁数据和布局数据,从选择性电离角度出发,推荐了Sn激光共振电离质谱分析中Sn电离光谱通道。     

Sn激光共振电离质谱分析中电离通道理论探讨

Sn激光共振电离质谱同位素分析中电离通道的选择非常关键.采用Dirac–Hartree–Fock(MCDHF)方法和相对论组态相互作用的Grasp VU原子结构计算程序,计算了Sn、Te原子的低激发态能级结构、光谱跃迁几率.通过对Sn质谱分析用灯丝样品进行热蒸发实验,确定了Sn原子在蒸发条件下基态能级粒子布局.结合理论计算跃迁数据和布局数据,从选择性电离角度出发,推荐了Sn激光共振电离质谱分析中Sn电离光谱通道.     

NaS分子4^2П→3^2Σ^＋跃迁光辐射特性的理论研究

应用“反射方法”计算了ＮａＳ分子４＾２П→３＾２Σ＾＋跃迁几率密度的分布，对其相应跃迁的自发辐射、粒子数反转、受激辐射等问题进行了理论上的探讨。     

Free-electron laser with the slow wave medium

One-dimension linear theory for free-electron laser with the slow wave medium is set up in terms of Fourier transform in the paper. The eigen fields for the free-electron laser are found and the derivation of the dispersion equations for interaction of electrons with the fields is made. The approximate and analytic expressions for the growth are given. Based on the eigen fields obtained, the mechanisms for the co-gyrotron synchronization and for the inverse-gyrotron synchronization are expounded.     

Generation of Intense THz Pulsed Lasers Pumped Strongly by CO2 Pulsed Lasers

A theoretical method dealing with two intense laser fields interacting with a three-level molecular system is proposed. A discussion is presented on the properties of the solutions for time-independent and time-dependent absorption coefficients and gain coefficient on resonance for strong laser fields, based on analytic evaluation of the rate equations for a homogeneously broadened, three-level molecular system. The pump intensity range can be estimated according to the analytic expression of pump saturation intensity. The effects of pulse width, gas pressure and path length on the energy absorbed from pump light are studied theoretically. The results can be applied to the analysis of pulsed, optically pumped terahertz lasers.     

Effects of applied electric and magnetic fields on the nonlinear optical rectification and second-harmonic generation in a graded quantum well under intense laser field

In this present study, the effects of electric and magnetic fields on the nonlinear optical rectification and second-harmonic generation in a graded quantum well under intense laser field have been investigated theoretically. The energy eigenvalues and their corresponding eigenfunctions are obtained by solving Schrödinger equation within the framework of effective mass approximation. The analytic expressions for the optical properties are calculated by the compact-density-matrix approach and iterative method. The numerical results are presented for a typical GaAs/Ga_1?x Al _x As quantum well. The results show that the nonlinear optical rectification and second-harmonic generation coefficients are considerably affected by the electromagnetic fields and intense laser field.     

Zeeman-tuned slowing of rubidium using σ and σ polarized light

Experimental results are presented for Zeeman-tuned slowing of an atomic rubidium beam in both the σ⁺ and σ⁻ polarized light configurations. A model of Zeeman slowing is applied to ideal magnetic fields, realistic fields, and the actual measured fields in order to clarify the similarities and differences between σ⁺ and σ⁻ slowing. The dependence of the final slowed velocity on the laser frequency detuning is studied and good agreement is found between the experimental results and both computer simulations and approximate analytic expressions.     

Semiclassical Dirac theory of tunnel ionization

We present analytic tunnel ionization rates for hydrogenlike ions in ultrahigh intensity laser fields, as obtained from a semiclassical solution of the three-dimensional Dirac equation. This presents the first quantitative determination of tunneling in atomic ions in the relativistic regime. Our theory opens the possibility to study strong laser field processes with highly charged ions, where relativistic ionization plays a dominant role.     

双波场共振泵浦的四能级原子系统

本文运用Dressed原子态方法;把四能级原子与两个激光场和一个探测场的相互作用转化为四能级原子与一个弱探测吸收场的相互作用,然后采用微扰理论求解Dressed原子表象中的密度矩阵方程,得出吸收谱的解析表达式,并详细讨论了吸收谱的各种持性.最后,导出了由外场感应的能级间的电偶极矩表达式,并找出了吸收谱与它的关系.     

Time-dependent alignment and orientation of molecules in combined electrostatic and pulsed nonresonant laser fields

We examine the time evolution of states created by the nonadiabatic interaction of a polar molecule with combined electrostatic and pulsed nonresonant laser fields and show that the orientation due to the electrostatic field alone can be greatly enhanced by restricting the angular amplitude of the molecule by the pulsed laser field. An analytic model indicates that in the short-pulse limit the interaction is governed by an impulsive transfer of action from the radiative field to the molecule.     

Nonparaxial elegant Laguerre-Gaussian beams

Closed-form nonparaxial expressions for optical beams are useful to calculate the fields produced by tightly focused laser beams. Such expressions for elegant Laguerre-Gaussian (eLG) beams that are exact solutions of the Helmholtz equation are introduced. These solutions are expressed as linear combinations of a finite number of analytic functions that involve spherical Bessel functions and associated Legendre functions of complex arguments. In the paraxial limit, the expressions proposed have the property to reduce to the well-known eLG beams.     

Structure of a laser field of various polarizations in the focal region of an ideal focusing lens. Calculation by methods of scalar diffraction theory

Within the framework of the scalar diffraction theory, we elaborate the method of calculating the electromagnetic-field structure in the ideal-lens focal plane. Using the method of quaternions for describing the rotation in three-dimensional space and diffraction integrals, we derive analytic formulas for the intensity distribution in the fields in the vicinity of the lens focal plane. We generalize the Debye method for an arbitrary polarization of the incident laser beam, in particular, for the linear, radial, and azimuthal polarizations. Such an approach, in view of the analytic formulas obtained, allows us to decrease the processing speed by an order. We show that the algorithm elaborated allows us to calculate the field amplitude?Cphase structure in the case of multimode laser radiation with a random phase.     

Dressed states analysis of lasing without population inversion in a three-level ladder scheme: Approximate analytic time dependent solutions

A dressed-state study of lasing without population inversion from a three level atom interacting with a bi-chromatic laser field, in the ladder configuration, is formulated. We allow the atomic system to be dressed by both laser filed photons (double dressing). The evolution of the system under consideration is being explored both analytically and numerically, within the transient regime. Time dependent approximate analytic solutions for dressed-state populations and coherences are derived, within the so called “secular approximation,” under resonant conditions. We also present time dependent numerical solutions for population and coherences in the off-resonance regime. A spectral analysis is also performed revealing the structure of various dressed states transitions. These are shown to be composed of quintets centered about the frequencies of the coupling and probe laser fields and having sidebands located symmetrically at positions shifted from line center at the Rabi and double Rabi frequencies.