Cs原子多光子过程的理论计算

采用Laplace变换讨论了多光子吸收过程中的跃迁几率与能级移位,并具体应用于计算Cs原子三光子吸收过程,得出了与实验相符的结果。     

多光子反Jaynes-Cummings模型中纠缠原子的布局数反转演化

利用多光子反Jaynes-Cummings模型研究了单模相干光场与两个全同的纠缠二能级原子相互作用时纠缠原子的布局数演化,并讨论相干光场的平均光子数及跃迁光子数对纠缠原子布局数产生的影响。结果表明：随着相干光场平均光子数的增加纠缠二能级原子处于激发态和基态的几率差减小,布局数的振荡曲线整体上移; 随着跃迁光子数的增加纠缠二能级原子处于激发态和基态的几率差增大, 振荡曲线整体下移。     

相位退相干对多光子过程中两原子纠缠的影响

利用全量子理论及部分转置矩阵负本征值的方法,研究了存在相位退相干时多光子T-C模型中两个二能级原子与数态光场相互作用系统中两原子的纠缠演化特性。讨论了相位退相干系数、原子间偶极-偶极相互作用系数、跃迁光子数对原子间纠缠演化特性的影响。结果表明：相位退相干因子并不能完全破坏两原子间的相干性,而是衰减了原子间纠缠度的振荡幅度。随着偶极相互作用系数的增大和跃迁光子数的增多,两原子最终处于纠缠度值较稳定的纠缠态;两纠缠原子的相干性越好,两原子越容易达到纠缠度值较大且稳定的纠缠态。     

受激喇曼过程中的脉冲压缩

论述实际喇曼过程中的双光子双稳态特性,讨论通常的喇曼脉冲的压缩机理。这种机理有可能实现可调谐的脉冲压宽技术。     

多光子Tavis-Cummings模型中运动原子与二项式光场相互作用的量子纠缠

利用全量子理论,研究了多光子Tavis-Cummings模型中运动原子与二项式光场相互作用系统的量子纠缠特性,讨论了不同初始状态下的二项式光场系数和原子运动速度对纠缠特性的影响.结果表明：二项式光场系数不影响场熵演化的周期性,但影响场熵峰值大小.随着原子跃迁光子数的增多,场熵演化的周期性和消纠缠现象逐渐消失.原子运动的速度影响场熵的演化周期,且影响场熵峰值的大小,而原子跃迁光子数的增大,会消弱原子运动速度对场熵演化的影响.当光场处于中间态,原子运动速度较低,且原子跃迁光子数较大时,光场与原子可以长久地处于量子纠缠态.     

Nonlinear optical processes in atoms and molecules using rare-gas halide lasers

The use of nonlinear optical processes expands the flexibility of excimer systems in the study of a wide range of atomic and molecular phenomena and materials. These mechanisms have already allowed for the selective excitation of states in the 10 to 20 eV range involving bound state excitation, ionization, and molecular dissociation. Specific examples involving the electronic excitation of H2, Kr, and Xe, the production of Xe⁺for the analysis of the molecular properties of XeF*, and nonlinear photodissociation of N2O and OCS are discussed.     

Correlation between stimulated scattering processes and laser-induced damage in crystalline quartz

The results of a systematic series of experiments to uncover possible correlation between laser-induced s.b.s. phonons and damage in quartz are presented. Such correlation is confirmed and the various thresholds established. The anomalous transmission factor under phonon generation is found to decay exponentially as predicted with increasing incident laser power. The l.f. s.b.s. phonon is also demonstrated to be a sensitive probe for precatastrophic damage.     

Pulsed stimulated emission from N, C, Cl, and F atoms

Eighteen electrically pulsed parent compound-helium mixtures yielded N, C, Cl, or F atom lasing. The laser pulses appeared as one or more peaks at each wavelength. New lasing on the chlorine wavelength (3.5443 μmvac) was observed from a Cl2-He mixture.     

双模相干场与Bell态原子多光子作用的原子布居数演化

应用全量子理论研究了非关联双模相干场与Bell态原子多光子相互作用过程中原子粒子布居差的时间演化规律.结果表明,当两原子初始处于1/√2(| ,-〉-|-, 〉)态时,原子粒子布居差恒为零;当两原子初始时刻的状态为其它三个Bell态时,原子粒子布居差的时间演化强烈依赖于原子间的偶极-偶极相互作用强度、场-原子间的耦合系数以及原子的跃迁光子数.随着原子间的偶极-偶极相互作用的增强,原子跃迁光子数的增加,原子布居差的时间演化中,Rabi振荡的频率都会明显加快,并且当原子间的偶极-偶极相互作用强度足够大时,原子布居差的崩塌-回复现象就会消失.     

Measurement of stimulated transverse mode mixing in a free electron laser

We report the first measurement of the off-diagonal terms in the transverse gain matrix in a free electron laser. We show that the higher order transverse modes stimulated in the FEL interaction diminish in amplitude as the electron beam size is increased, that the far field and the near field effects of the excited modes are not equivalent, and that in this low divergence case, the mode mixing is insensitive to the resonance parameter. Remarkably close agreement is demonstrated with the theory [1]. The effects of a multiple mode input beam are also observed, and the theoretical expression is derived.     

A mechanism of low-temperature stimulated processes in plasma anodization of metals and semiconductors

A mechanism of stimulation of low-temperature plasma anodization using a catalyst or ultraviolet radiation in the case of the formation of oxide films of metals and semiconductors is suggested. The stimulating effect of a catalyst or ultraviolet radiation on the process of plasma anodization is attributed to the appearance of an additional concentration of antibonding quasiparticles (electrons and holes) that weaken the chemical bonds in the anodized material. The conditions for implementing the stimulated processes are reported.     

The effect of temperature on the isotopic selectivity and decomposition yield of infrared multiphoton processes

In this paper we assess the effect of substrate temperature on the isotopic selectivity and dissociation yield of multiphoton dissociation of hexafluoroacetone and trifluoromethyl chloride. In the former molecule, the temperature effects are due to the contribution of vibrational hot bands; in the latter, these effects are overlaid on the kinetic mechanism resulting in a loss of yield of carbon-13 bearing products.     

双模纠缠相干场与原子多光子相互作用系统的原子布居数演化

利用全量子理论并结合数值计算的方法,研究两个二能级原子与双模纠缠相干场相互作用系统的原子布居数演化性质.讨论了跃迁光子数、初始平均光子数、光场纠缠程度及双原子问偶极相互作用对原子布居数演化特性的影响.     

双光子共振激发的电离复合产生受激电子辐射

文中报道利用双光子共振激发锂原子到4s态,获得了多条受激电子辐射和相干辐射,同时观察到了高于4s能级的nd,ns态(n≥4)到2p态的跃迁,以及从连续态到3s态的辐射。     

266nm激光作用下1,3-二溴苯的多光子电离和解离研究

在波长为266 nm的激光作用下对1,3-二溴苯分子的多光子电离解离过程进行了研究,获得了溴苯分子的MPIF-TOF质谱,并测得了各碎片离子占总离子信号的百分比对激光强度的依赖关系.用这些实验结果分析1,2-二溴苯分子的多光子电离解离机理,得出1,3-二溴苯的MPI过程主要是母体分子解离-中性碎片电离C6H 4,C5H 3,C4H 2,C3H 等碎片离子主要是经过离子离解阶梯模式产生的,并给出了可能的解离通道.     

The prospects of an X-ray free electron laser using stimulated resonance transition radiation

This paper considers stimulated X-ray emission from a relativistic beam of electrons passing through a periodic, heterogeneous medium and interacting with a plane wave. Amplification of the wave occurs when there is bunching of the electrons due to this interaction. The gains for warm and cold electron beams are derived neglecting space charge and multiple scattering. High-current, ultrarelativistic electron beams appear to be the most likely to produce reasonable gain. An estimate of the multiple scattering for the examples cited show the net gain to be severely affected.     

The role of excited states in multiphoton ionization

The mixing of the excited states of an atom with the ionization continuum is considered by a modification of Fano's theory of autoionization. It is shown that in the case of the noble gases this leads to a reduction of the threshold power-law indexKfromI/hbaromegatoE_{n}/hbaromega(whereIis the ionization energy, Enthe lowest excited state energy, andhbaromegathe photon energy) as found experimentally.     

Analysis of free processes in time varying circuit by means of generalized characteristic equations method

Developing methods of analysis of free processes in time varying circuit is important both for time varying and nonlinear radio circuits. The principle of linear connection brings together processes in time varying and nonlinear circuits. It is of special interest to extend the existing methods developed for radio circuits with stable parameters to time varying circuits. This article is devoted to one of such methods-the method of characteristic equations for differential equations with fixed factors.     

半导体材料中的多光子吸收效应研究进展北大核心CSCD

一般情况下半导体材料可以吸收一个能量大于带隙的光子,使价带中的一个电子跃迁到导带。但是,在某些特殊的情况下,半导体材料也能吸收多个能量小于带隙的光子,使价带中的一个电子跃迁到导带,这就是多光子吸收效应。多光子吸收效应是一种非线性光学效应。该综述首先介绍了多光子吸收效应的理论基础和测试方法,然后回顾了多光子吸收效应的研究成果,最后展望了半导体低维结构中的多光子吸收效应研究,以及潜在的应用前景。