激发态H2(X1∑+g,v=1,J=1)之间的碰撞能量合并

受激拉曼激发H2(0,1)基态的Q支得到H2(1,1)能级.在室温条件下,利用反斯托克斯拉曼散射(CARS)探测技术测量了碰撞能量合并(EP)过程H2(1,1)+H2(1,1)→H2(2,J)+H2(0,J″)及H2(1,1)与H2(1,J)转动能级间的碰撞转移速率系数.扫描CARS谱表明在H2(1,1)能级的碰撞能量...     

Tunable chirped microwave photonic filter employing a dispersive Mach-Zehnder structure

A Mach-Zehnder structure with modulation in one arm and dispersive time delay in the other is proposed to implement highly flexible single-bandpass chirped microwave photonic filters based on broadband optical sources. Both the amplitude response and the time delay slope can be fully reconfigured via control of the optical spectra and dispersion. The passband can also be widely tuned without changing the shape. A chirped filter with a bandwidth of ～4?GHz, a delay slope of ～-0.6?ns/GHz, and a tunability up to 40?GHz is demonstrated experimentally.     

Experimentally Determining Bloch Parameters of Hamiltonian for Single-Qubit Systems

By considering the identification problem of unknown but fixed Hamiltonian H = S0σ0 ＋∑i=x,y,z Siσi where σi （i = x, y, z） are pauli matrices and σ0=I, we explore the feasibility and limitation of empirically determining the Hamiltonian parameters for quantum systems under experimental conditions imposed by projective measurements and initialization procedures. It may be unsurprising to physicists that one can not obtain the knowledge of So no matter what kind of projective measurements and initialization are permitted, but the observation draws our attention to the importance of the parameter identifiability under different experimental condition. It has also been revealed that one can obtain the knowledge of ｜Sz｜ and Sx^2＋Sy^2 at most when only the projective measurement {｜0/（0｜, ｜1/（1｜} is permitted to perform on and initialize the qubit. Further more, we demonstrated that it is feasible to distinguish ｜Sx｜, ｜Sy｜, and ｜Sz｜ even without any a priori information about Hamiltonian if at least two kinds of projective measurement or initialization procedures are permitted. It should be emphasized that both projective measurements and initialization procedures play an important role in quantum system identification.     

Phase mismatching analysis of third-harmonic generation in BBO crystal

<正>Phase mismatching for third-harmonic generation(THG) in barium metaborate(BBO) crystal is investigated in detail.Upon using BBO crystal in the TypeⅠ(oo→e) scheme,in the two independent planes (principal section of the crystal and the plane normal to principal section),when the input second-harmonic beam deviates from the expected direction,phase mismatching occurs and the angle deviation produces different effects on the conversion efficiency.We numerically simulate these two cases of phase mismatching and identify the relation between the conversion efficiency and the deviation angle in the air.The computational results indicate that the phase matching tolerance in the principal section is 0.2°(in the air),while the phase matching tolerance in the plane normal to principal section is 4.5°(in the air).After conducting a lab experiment,the results agree perfectly with the computational results,indicating that the deviation angle in the principal section has a greater effect on the conversion efficiency.     

新型热声谐振机构的理论分析和实验验证

谐振管作为热声发动机的重要组成部分,其长度占整个系统轴向长度的大部分。本文提出了一种利用液体和弹性膜组成谐振系统的方法,并使用这种谐振系统取代谐振管,使系统轴向尺寸减少为原来的1/5。文中利用线性热声理论对该谐振系统的谐振频率进行了计算,并对不同阻尼系数对系统的耗散做出了分析。实验结果表明,在利用驻波热声发动机驱动的情况下,谐振系统自激起振,谐振频率为360 Hz,实际谐振频率与计算值误差在5%以内。     

流动管道内利用旁通管道反声降噪研究

降低流动管道噪声在工程上是非常有用的。本文应用线性声学理论将无流动时旁通管道反声降噪方法推广到具有流动的情况,进行了数值计算和实验研究。数值工作包括建立相应的声学关系和管道分叉点连接条件;计算了多种噪声源传声损失频率特性,并讨论了主要参数对反声的影响。实验研究是对单段旁通管道有吸声尖劈的情况下进行的,实验时采用不同的噪声源和不同的流速,测量结果与理论计算符合良好。     

THEORETICAL RESEARCH ON OPTICAL,THERMAL AND MAGNETIC PROPERTIES OF DICHLOROTETRAPY-RAZOLENICKEL(TYPE II)COMPLEX

In this paper, we have calculated and analyzed theoretically and consistently the absorption spectra, the ZFS and EPR parameters of the ground state, the Schottky low-temperature heat capacity, and the paramagnetic susceptibility of Ni(pz)₄Cl₂ (Dichlorotetrapyrazolenickel) complex by using d⁸[(1-C₂)D^*_4h+C₂D^*_2h] complete configuration mixing unified crystal field theory. The theoretical results agree with the experimental observation very well. We can give a complete and reasonable theoretical interpretation of the optical, thermal and magnetic properties of Ni(pz)₄Cl₂.     

Excitation Transfer for K2 in High-Lying States by N2

A K-N2 mixture is irradiated in a glass fluorescence cell with pulses of 710hm radiation from an OPO laser, populated K2 （^1∧g） state by two-photon absorption. The cross section for ^1∧g →^3∧g transfer in K2 is determined using molecular fluorescence spectrometry. The cell temperature is kept constant at 553K. The N2 pressure is varied between 40 Pa and 400 Pa. The effects of K2-K collisions could not be neglected. These effects are subtracted out by using the results of the pure K experiment. The cross sections are （3.8 ± 1.5） ×10^-15 cm^2 for K2 （^1∧g） ＋ N2 → K2（^3∧g） ＋N2 and （8.9 ± 3.5） × 10^-15 cm^2 for K2 （^3∧g） collisions with N2.     

Rb与H_2的反应碰撞:Rb(6~2D)+H_2→RbH+H

在样品池条件下,应用脉冲激光的泵浦-检测技术,研究了Rb(6~2D)激发态原子与H_2反应碰撞生成的RbH分子的振转能级的布居数密度分布及平均转动能、振动能、平动能的相对比值.发现RbH(X~1∑~+)只有v=0,1上有布居.转动带分布轮廓与池温下的统计分布接近,得到RbH的Boltzmann转动温度稍低于池温,而振动温度高.v=1和v=0上的布居数之比约为0.69,从而得到RbH(X~1∑~+)上平均转动能和平均振动能,由反应的有效能得到平均平动能,这三种能量的相对比值f_R:f_V:     

基于受激布里渊散射的波长间隔可变多波长光纤激光器

提出了一个基于自激发受激布里渊散射的波长间隔可变多波长光纤激光器.利用单模光纤中自激发产生的非线性布里渊增益和掺铒光纤的线性增益组成混合增益光纤激光器,从而使光纤激光器在室温下产生稳定的多波长输出.改变双折射光纤环镜滤波器中保偏光纤的长度,可以实现波长间隔可变多波长激光产生,提高了多波长光纤激光器操作的灵活性和实用性.实验实现了波长间隔从0.8nm至0.076nm可变的多波长激光产生,波长数随波长间隔减小而增加,间隔为0.08nm的激光波长数达86.