电子散射的钠原子受激态取向参数研究

原子碰撞中的取向(orientation)参数的研究为原子碰撞动力学、原子受激态结构提供了丰富的信息.散射靶原子集合可用态多极(state multipole)描述，用它可以表征受激态原子的取向参数.通过取向参数与受激原子态退激的偶极辐射光子的Stokes参数之间的关系，可以进行实验与理论的比较.本文主要研究钠原子受电子散射S→P跃迁中取向参数，根据散射理论的扭曲波近似展开计算得到的散射振幅，带入态多极，然后计算钠原子3P态取向与散射角的关系及不同入射能下受激态取向参数变化特点，并与电子-光子符合散射实验所测数据进行比较.考虑到符合散射实验的测量困难，在误差范围内，理论分析与实验结果符合得比较好. 关键词： 取向参数 态多极 Stokes参数 电子-光子符合测量     

极化电子与原子散射的广义Stokes参量的实验测量

分析了极化电子与原子散射后的受激原子退激辐射光的广义Stokes参量，介绍了Stokes参量的基本概念和实验测量方法并阐明其具体的物理意义．为自旋极化电子参与的原子或分子碰撞实验和理论模型的研究奠定基础．     

原子受激态的Stokes参数分析

根据密度矩阵理论,导出了受激原子态P态密度矩阵元和P态退激辐射的光子密度矩阵元的Stokes参数,它们之间存在一种非常简单直接的关系,说明在电子-光子符合散射实验中,通过测量光子的Stokes参数,就可以描述受激P态电荷云分布和散射过程的动力学。According to the density matrix theory, the density matrix of photon emitted from excited atom P state and of P state were introdued in this paper. There were a simple direct relation between the two density matrices, which shows that the electron cloud shape of excited atomic state and scattering dynamics can be described through the observable Stokes parameters of photon in electron-photon coincidence experiment.     

电子散射的受激原子态取向的趋向性规则

原子碰撞中的取向参数的研究为原子碰撞动力学、受激原子态结构提供了丰富的信息.本文介绍近年来电子与原子碰撞受激原子态取向的特征,其中包括电子与轻原子低能小角度散射下取向的趋向性规则;自旋依赖的取向特点;重原子散射下的取向特点,就重原子散射下取向的趋向性规则的破坏做了简要的分析和讨论.     

电子散射的受激原子态取向的趋向性规则

原子碰撞中的取向参数的研究为原子碰撞动力学、受激原子态结构提供了丰富的信息。本介绍近年来电子与原子碰撞受激原子态取向的特征，其中包括电子与轻原子低能小角度散射下取向的趋向性规则；自旋依赖的取向特点；重原子散射下的取向特点，就重原子散射下取向的趋向性规则的破坏做了简要的分析和讨论。     

电子与氦原子激态碰撞速率的光谱法研究

在电子密度5×10~(14)cm~(-3),电子温度1.1eV的氦等离子体中,用激光共振荧光,敏化荧光和激光“烧通”三种光谱技术,研究了电子与激态氦原子的碰撞速率.并与以文献上沿用的电子碰撞速率为基础的氦原子的多能级碰撞和辐射模型的计算进行了比较,发现该模型在很大程度上不能预言此类等离子体的特性.实验结果表明,氦原子激态间的电子碰撞转移速率的实际值远比理论值低.     

高电荷态离子入射Al表面库仑势对靶原子特征谱线强度的影响

用同一动能(150keV)而不同电荷态的⁴⁰Ar^q+(8≤q≤16)离子入射金属Al表面，靶原子受激辐射产生特征光谱线. 实验结果表明：高电荷态离子与金属表面相互作用过程中，经过与靶原子碰撞(Penning碰撞)交换动能和共振电子俘获(resonant capture)释放库仑势能，将携带的能量沉积于靶表面，使靶原子激发. 这种激发不同于光激发，它不仅激发了原子复杂电子组态之间的跃迁，而且跃迁辐射的特征谱线强度增强的趋势与入射粒子的库     

共轭聚合物中受激吸收与受激辐射的量子动力学研究

基于扩展的一维SSH紧束缚模型结合非绝热的分子动力学方法,理论研究了共轭聚合物分子(PPV)在光脉冲作用下受激吸收和受激辐射的量子动力学过程.首先,设定分子初始处于基态,讨论了受激吸收过程中不同的电子受激跃迁模式与光激发脉冲的关系.通过对终态的分析,发现分子受激后只能产生电子-空穴的束缚态,包括:激子、双激子和高能激子.计算了各种激发态的产率,特别是,给出了各种激发态产率与光激发能量的定量关系.此外,基于实验,分别讨论了光激发强度对高能激子和双激子产率的影响,并与实验结果进行了比较.最后,设定分子初始分别处于激子和双激子态,研究了分子内定域能级之间的受激辐射过程,并简单讨论了激子和双激子受激辐射与光激发能量及强度的关系.     

高电荷态离子入射Al表面库仑势对靶原子特征谱线强度的影响

用同一动能(150keV)而不同电荷态的⁴⁰Ar^q+(8≤q≤16)离子入射金属Al表面,靶原子受激辐射产生特征光谱线. 实验结果表明：高电荷态离子与金属表面相互作用过程中,经过与靶原子碰撞(Penning碰撞)交换动能和共振电子俘获(resonant capture)释放库仑势能,将携带的能量沉积于靶表面,使靶原子激发. 这种激发不同于光激发,它不仅激发了原子复杂电子组态之间的跃迁,而且跃迁辐射的特征谱线强度增强的趋势与入射粒子的库 关键词： 高电荷态离子 库仑势 特征光谱 光谱强度     

在钠原子-分子系统中氩气参与的碰撞能量转移过程

我们报道了钠原子-分子系统有惰性气体氩原子参与的碰撞能量转移过程.观察到了由此而产生的分子单重态和三重态的紫区受激辐射.实验结果表明,氩原子参与的碰撞能量转移过程在适当的氩气气压下起到了有利的作用,但过高的气压会使布居的粒子数减少,起到荧光淬灭效应.我们利用瞬时速率方程拟合了实验结果,得到了部分相同的变化规律.     

Quantal density functional theory of excited states

We explain by quantal density functional theory the physics of mapping from any bound nondegenerate excited state of Schr?dinger theory to an S system of noninteracting fermions with equivalent density and energy. The S system may be in a ground or excited state. In either case, the highest occupied eigenvalue is the negative of the ionization potential. We demonstrate this physics with examples. The theory further provides a new framework for calculations of atomic excited states including multiplet structure.     

Simple cases of spontaneous emission from an atom-photon cluster localized in a microcavity

The spontaneous emission from an atomic ensemble localized in a microcavity with the participation of microcavity photons and an external broadband quantized electromagnetic field at the Raman resonance of photons with an optically forbidden (two-photon) atomic transition has been studied. The average spontaneous decay intensity has been calculated for simple cases. It is shown that the dynamics of spontaneous emission from this atomic ensemble differs generally from the conventional superradiance (spontaneous emission of an atomic ensemble at a one-photon optically allowed transition from excited to the ground state. When the atomic ensemble is strongly excited, the delay times and the emission pulse shape differ significantly. The parameter ranges where the spontaneous emission from the atomic ensemble under consideration at a two-photon Raman transition can be described as conventional superradiance with renormalized parameters are found. In the case of single excitation the photon emission probability depends on the number of photons and atoms in the microcavity.     

Dynamic electronic after-effects of nuclear decay in Mössbauer resonances

A theory has been constructed for the effect of a decaying atomic state on the Mössbauer line shapes. A most general case has been considered in which the nucleus interacts with its surroundings via electric monopole as well as electric quadrupole and magnetic dipole coupling, and the decay of the excited atomic state results in a change in the direction of the quantization axis.     

Quantum State Transfer Between Any Pair of Qubits in a Quantum Network via Optical Fibers

We propose scheme for transferring quantum state between any pair of nodes in a quantum network. Each node consists of an atom and a cavity, with the atom acting as the quantum bit. Any two adjacent nodes are connected by an optical fiber. During the operation neither the atomic system nor the fibers are excited, which is important in view of decoherence. Under certain conditions, the probability that the cavities are excited is negligible. The method has an inherent robustness against the fluctuation perturbations in the classical control parameters and the randomness in the atomic position. The scheme can be generalized to implement quantum phase gate between any two remote qubits.     

Lasers as Light Sources for Analytical Atomic Spectrometry

Abstract

Lasers have advantages compared to conventional light sources, which include high power, a monochromatic emission profile, stability, and rapid tuning across an atomic line. These advantages have resulted in superior analytical figures of merit and methods of background correction compared to conventional light sources. The most widely used lasers for atomic spectrometry include dye laser systems, optical parametric oscillator systems, and diode lasers. Three principal techniques employ lasers as light sources. Laser‐excited atomic fluorescence spectrometry (LEAFS) involves the use of laser light to excite atoms that emit fluorescence and serves as the analytical signal. Laser‐enhanced ionization (LEI) involves laser excitation of atoms to an excited state energy level at which collisional ionization occurs at a higher rate than from the ground state. Diode laser atomic absorption spectrometry (DLAAS) employs a DL as a source to excite atoms in an atom cell from the ground state to an excited state. The analytical signal is involves the ratio of the incident and transmitted beams. Recent applications of these techniques are discussed, including practical applications, hyphenated techniques employing laser‐induced plasmas, and work to characterize fundamental spectroscopic parameters.     

Zum Nachweis von änderungen im angeregten Zustand eines Atoms durch Beobachten der folgenden änderungen im Grundzustand

Radio frequency transitions in the excited state of Rb atoms are observed by measuring the transmitted light in a resonance cell experiment. The influence of additional radio frequency transitions simultaneously performed between the Zeeman sub-levels of the ground state is studied. Methods for observing signals of the excited states without using fluorescent light as detector are discussed concerning the magnetic deflection of optical oriented atoms and also the influence of recoil of the scattered light quants on the direction of an atomic beam.     

Inversion of an Atomic Wave Packet in a Circularly Polarized Electromagnetic Wave

We study behavior of an atomic wave packet in a circularly polarized electromagnetic wave,and particularly calculate the atomic inversion of the wave packet.A general method of calculation is presented.The results are interesting.For example,if the wave packet is very narrow or /and the interaction is very strong,no matter the atom is initially in its ground state or excited state,the atomic inversion approaches zero as time approaches infinity.If the atom is initially in its ground state and excited state with the probability 1/2 respectively,and if the momentum density is an even function,then the atomic inversion equals zero at any time.