Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference （CQI） was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken,from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.     

The differential interference angle in collisional quantum interference on rotational energy transfer

Collisional quantum interference （CQI） in the intramolecular rotational energy transfer was observed in experiment by Sha and co-workers. The interference angle, which measuring the degree of the coherence, were measured in the experiment of the static cell. Based on the first Born approximation of time dependent perturbation theory, taking into accounts the anisotropic Lennard-Jones interaction potentials, this paper describes the theoretical model of CQI in intramolecular rotational energy transfer in an atom-diatom collision system. In the model, the differential interference angle for the experiment of the molecular beam is calculated, the changing tendencies of the differential interference angle with the impact parameter and collision partners are obtained. This theoretical model is important for understanding or performing this kind of experiments.     

The differential interference angle of ^2∏[Case（a）] diatom on rotational energy transfer in NO（X^2∏） collision with He,Ne and Ar system

To study theoretically the relationship between the differential interference angle and the scattering angle in collisional quantum interference （CQI）, we have investigated the differential interference angle of the atom-diatomic [case（a）] molecule system in detail. For the 2∏ electronic state in Hund＇s case （a）, the degree of the differential interference is also discussed. The differential interference angles of NO（X^2∏） are calculated quantitatively for the rotational energy transfer in Hund＇s case （a） induced by collision with He, Ne and Ar atoms. The method to calculate the differential interference angle is presented. Several factors that affect the differential interference angle are investigated. Finally the variation of the differential interference angle with the impact parameter and relative velocity is discussed.     

Further Study of A-Related Quantum Interference of H-State Diatomic on Collision-Induced Rotational Energy Transfer

In our previous theoretical studies [Meng-Tao Sun, Yong-Qing Lee, and Feng-Cai Ma, Chem. Phys.Left. 371 （2003） 342], we have reported the quantum interference on collision-induced rotational energy transfer on CO （A ^1 Π,v = 3） with inert gases, which originates from the difference between the two A-related collision potential energy surfaces. The interference angle, which measures the degree of coherence, is presented in this paper. Based on the time-dependent first order Born approximation, taking into account the anisotropic Lennard-Jones interaction potentials, the relation of the interference angle with the factors, including experimental temperature, partner, and rotational quantum number, are obtained. The changing tendencies with them are discussed. This theoretical model is important to understanding and performing this kind of experiment.     

Influence of mode competition on beam quality of fiber amplifier

Theoretical and experimental studies of the influence of the mode competition on the output beam quality of fiber amplifiers are presented. Rate equations and modal decomposition method are used in the theoretical model. In the experiment, the output beam-quality factor of a fiber amplifier, which is based on a Yb-doped double-clad large mode area fiber as a function of the seed beam quality and the pump power of the amplifier, is measured. The experimental results are consistent with the theoretical analysis.     

Interference Angle on Quantum Rotational Energy Transfer in Na＋Na2 （A1 ∑u^＋,v=8-b^3∏0u,v=14） Molecular Collision System

In order to study the collisional quantum interference （CQI） on rotational energy transfer in atom-diatom system, we have studied the relation of the integral interference angle and differential interference angle in Naq-Na2 （A1 ∑u^＋,v=8-b^3∏0u,v=14） collision system. In this paper, based on the first-Born approximation of timedependent perturbation theory and taking into accounts the anisotropic effect of Lennard-Jones interaction potentials, we present a theoretical model of collisional quantum interference in intramolecular rotational energy transfer, and a relationship between differential and integral interference angles.     

Further Study of A-Related Quantum Interference of П-State Diatomic on Collision-Induced Rotational Energy Transfer

In our previous theoretical studies [Meng-Tao Sun, Yong-Qing Lee, and Feng-Cai Ma, Chem. Phys.Lett. 371 (2003) 342], we have reported the quantum interference on collision-induced rotational energy transfer on CO (A1П, v = 3) with inert gases, which originates from the difference between the two A-related collision potential energy surfaces. The interference angle, which measures the degree of coherence, is presented in this paper. Based on the time-dependent first order Born approximation, taking into account the anisotropic Lennard-Jones interaction potentials, the relation of the interference angle with the factors, including experimental temperature, partner, and rotational quantum number, are obtained. The changing tendencies with them are discussed. This theoretical model is important to understanding and performing this kind of experiment.     

Compact all-optical switches based on photon-induced suppression of mode interference

An optically activated optical switch based on suppression of mode interference (SMI) is presented. The imaging properties of multi-mode interference (MMI) section in the switch with Y-branch can be modified by a controlling light injection. The switch was simulated by finite difference beam propagation method (FD-BPM) and fabricated on GaAlAs/GaAs epitaxial materials. At the wavelength of 1.31 μm, the primary experiment showed an extinction ratio of about 8 dB with controlling light power density of 73.5 W/mm2.     

Distortion of optical feedback signals in microchip Nd:YAG lasers subjected to external multi-beam interference feedback

This paper proposes a theoretical analysis for the characteristics of an external cavity Nd:YAG laser with feedback of multiple-beam interference, which is induced by the multi-reentrance of the light from the external Fabry--Perot cavity. The theoretical model considers the multiple beam interference of the external Fabry--Perot cavity. It is found that the optical feedback signals are distorted to pulse waveforms instead of the sinusoidal ones in conventional feedback. The experimental results are in good agreement with the theoretical analysis. The obtained theoretical and experimental results can advance the development of a laser feedback interferometer.     

Effects of Arbitrarily Directed Field on Spin Phase Oscillations in Biaxial Molecular Magnets

Quantum phase interference and spin-parity effects are studied in biaxial molecular magnets in a magnetic field at an arbitrarily directed angle.The calculations of the ground-state tunnel splitting are performed on the basis of the instanton technique in the spin-coherent-state path-integral representation,and complemented by exactly numerical diagonalization.Both the Wentzel-Kramers-Brillouin exponent and the pre-exponential factor are obtained for the entire region of the direction of the field.Our results show that the tunnel splitting oscillates with the field for the small field angle,while for the large field angle the oscillation is completely suppressed.This distinct angular dependence,together with the dependence of the tunnel splitting on the field strength,provides an independent test for spin-parity effects in biaxial molexular magnets.The analytical results for the molecular Fes magnet are found to be in good agreement with the numerical simulations,which suggests that even the molecular magnet with total spin S=10 is large enough to be treated as a giant spin system.     

转动传能量子干涉效应:干涉角影响因素的研究

碰撞转动传能中存在量子干涉效应已经在静态池实验中被观测到,并且积分角也能被测量.利用分子束实验可得到转动传能更准确的信息,进而得到影响干涉角的的具体因素.文中利用一阶含时波恩近似和L-J相互作用势,建立了原子—双原子分子碰撞系统转动传能的量子干涉模型,描述了观察和测量微分干涉角的方法,得到了微分干涉角与碰撞半径和碰撞速度间的关系,同时也得到了积分干涉角和实验温度的关系.此理论模型对于理解和进行分子束实验是非常重要的.     

深入理论研究碰撞转动传能量子干涉效应的微分干涉角

分子内部转动传能的静态池实验观察到了碰撞量子干涉效应(CQI),并且测得积分干涉角,为了获得更加精确的分子内部转动传能的碰撞量子干涉效应信息,实验就必须要采用分子束实验进行.本文理论上采用各项异性相互作用势,应用含时微扰理论的一级波恩近似,假想在分子束实验的条件下,建立在原子—双原子分子体系中碰撞量子干涉的理论模型.理论上推导出微分干涉角具体表达式,通过计算定性地讨论了微分干涉角随着碰撞参数、速率等的变化趋势,同时初步探讨了实验的正确观测途径,得出了采用分子束进行实验观测的实验方法,为进一步进行分子束实验提供了理论基础,对实验的进行起到了一定的借鉴作用.     

Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference (CQI) was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken, from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.     

量子干涉效应中干涉角和散射角的研究

利用波恩近似理论对双原子激发态转动传能进行了剖析,更深入的研究了原子分子碰撞过程中量子干涉效应相关信息．利用各项异性相互作用势和直线轨迹近似建立了新的量子干涉模型,讨论了原子与分子碰撞时散射角和微分干涉角的关系,得到了干涉角和各向异性参数及转动量子数的关系．     

Na2(A1∑u+,v=8～b3Ⅱ0u,v=14)-Na体系转动传能的碰撞量子干涉效应

沙国河及其工作组于1995年发表了CO A1Π(v=0)～e3∑-(v=1)与He1,Ne及其它碰撞伴的碰撞过程中转动传能的碰撞量子干涉现象,并得到了积分干涉角,陈等从理论和实验上发现了Na2(A1∑u ,v=8～b3Π0u,v=14)体系与Na(3s)碰撞的碰撞量子干涉现象,孙等计算了其积分干涉角,但是对微分干涉角没有过多的计算.本文作为对原子-双原子体系碰撞诱导转动传能的进一步理论研究,在含时一级波恩近似的基础上考虑各向异性相互作用势和长程相互作用势,计算了单叁混合态的Na2(A1∑u ,v=8-bΠ0u,v=14)体系与Na碰撞的微分干涉角,并得到了微分干涉角与碰撞参数的关系,此理论模型对理解和进行分子束实验是非常重要的.     

Interference Angle on Quantum Rotational Energy Transfer in Na+Na2 (A1 Σ+u,v=8∽ b3 Π0u,v=14) Molecular Collision System

In order to study the collisional quantum interference (CQI) on rotational energy transfer in atom-diatom system, we have studied the relation of the integral interference angle and differential interference angle in Na+Na₂ (A¹Σ^+_u, v=8∽b³Π_0u, v=14) collision system. In this paper, based on the first-Born approximation of time-dependent perturbation theory and takinginto accounts the anisotropic effect of Lennard-Jones interaction potentials,we present a theoretical model of collisional quantum interference inintramolecular rotational energy transfer, and a relationship betweendifferential and integral interference angles.     

双向剪切干涉法测量高斯光束远场发散角

对双向剪切干涉理论和高斯光束传输特性进行了研究.提出了一种测量高斯光束远场发散角的方法：利用双向剪切干涉仪分别在激光传输路径上两个特定位置测出波前曲率半径,然后由曲率半径得出发散角.通过理论推导建立了相应的检测模型,并对模型进行了实验验证.实验测量和误差分析表明该方法的测量准确度能达到10″;发散角测量准确度的主要影响因素为干涉条纹宽度测量误差.