弱射频场中Rydberg原子的电磁感应透明

在铯原子室温蒸气池中研究了弱射频场中Rydberg原子阶梯型三能级系统的电磁感应透明(EIT)效应.铯原子基态6S_(1/2)、第一激发态6P_(3/2)和Rydberg 48D_(5/2)态形成阶梯型三能级系统,探测光共振作用于6S_(1/2)(F=4)→6P_(3/2)(F′=5)的跃迁,耦合光在Rydberg跃迁线6P_(3/2)(F′=5)→48D_(5/2)附近扫描,形成Rydberg原子EIT.当对铯原子施加一个80 MHz的弱射频电场时,48D_(5/2)Rydberg原子的EIT光谱发生Stark频移和分裂,同时产生由射频场调制Rydberg能级的偶数级边带,测量结果与Floquet理论模拟的结果相符合.同时,改变弱射频电场的频率研究了铯Rydberg能级的自电离效应对Rydberg原子Stark谱的影响,据此,我们提出将电极板置于铯原子蒸气池内的方案以减少自电离效应的影响.在弱射频Stark谱中,mj=5/2的Stark谱与mj=1/2,3/2的二级边带形成多个能级交叉,这些能级交叉点提供了一种基于原子的精确校准射频电场的新方法.     

Generation of entangled TEM_(01) modes with periodically poled KTiOPO_4 crystal

Spatial quantum optics based on the high-order transverse mode is important for the super-resolution measurement and quantum image beyond the shot noise level. Quantum entanglement of the transverse plane Hermite–Gauss TEM_(01) mode has been demonstrated experimentally in this paper. Two squeezed TEM_(01) modes, which are generated by a pair of degenerate optical parametric amplifiers(DOPA) with the nonlinear crystals of periodically poled KTi OPO_4, have been combined to produce TEM_(01) mode entanglement using a beam splitter. The 1.5 dB for the sum of amplitude and 1.2 dB for the difference of phase below shot-noise level is achieved with the measurement system of a Bell state detection.     

平衡零拍平移测量实验研究

利用平衡零拍探测方法对TEM00模相干光激光束的微小平移进行一维测量的实验研究,实验装置最小可测平移量为0.3nm.实验验证了平移与倾斜这两个物理量之间的共轭关系.最后用模式重叠的概念分析了本底光偏离标准的TEM10模对测量结果的影响.实验结果与理论基本符合.     

Lagrange multiplier method used in BESⅢ

In this paper, the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment. First we introduce the Lagrange multiplier method and implement kinematic constraints. Then we present the performance of the kinematic fitting algorithm. With the kinematic fitting, we can improve the resolution of track parameters and reduce the background.     

Lagrange multiplier method used in BESⅢ kinematic fitting

In this paper,the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment.First we introduce the Lagrange multiplier method and implement kinematic constraints.Then we present the performance of the kinematic fitting algorithm.With the kinematic fitting,we can improve the resolution of track parameters and reduce the background.     

An Original Monomer Sampling from a Ready-Made Aβ42 NMR Fibril Suggests a Turn-β-Strand Synergetic Seeding Mechanism

Aggregation of amyloid beta (Aβ) is a central step of Alzheimer's disease. Aβ42 monomers are building blocks in the formation of both “on pathway” intermediate structures and “off pathway” oligomers. How to sample an Aβ monomer becomes a problem however due to the instinct of Aβ high flexibility and diversity as well as aggregation propensity. Currently, (1) most samplings focus on either the ready-made helix-rich 1Z0Q/1IYT NMR structure, or the completely extended conformation, but (2) few on a ready-made Aβ NMR fibril (i. e., 2BEG). Here we compare the simulation results from sampling in scheme (1) with that in scheme (2), and find that the coil and β-sheet contents in the 1Z0Q-sampled system are comparable to the counterparts in the 2BEG-sampled system, but with a large difference in simulation time and dynamics character. 1Z0Q-sampled system not only takes several times longer than the 2BEG-sampled one, and only β1-seeding dynamics characteristic is observed probably due to far insufficient conformation transition in the limited simulation time. Two dynamics characteristics of Aβ42 folding observed experimentally, that either β1 region or β2 region aggregates first, reproduce in the present simulations for 2BEG-sampled system however, suggesting a preferential sampling in the future simulation. In addition, a turn-β-strand synergetic seeding mechanism of aggregation is first proposed based on the trajectory analyses on the four regions of Aβ42 chain.     

一种共轭聚合物单分子发色团吸收和发射特性动态演变过程的实时测量

利用频域信息重构的散焦宽场成像测量了Poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole](PFO-DBT)共轭聚合物单分子发色团的吸收与发射特性及其动态演变过程.通过调制用于激发共轭聚合物单分子的超短脉冲对的相对相位,对单分子荧光进行傅里叶变换的频域测量,跟踪发色团吸收偶极取向变化;通过测量散焦荧光成像光斑探测发色团发射偶极取向变化.研究发现, PFO-DBT共轭聚合物单分子发色团存在吸收和发射偶极取向均保持不变、其中之一变化以及两者同时变化三种情况.这种对共轭聚合物单分子发色团吸收和发射偶极取向演化过程的实时测量可用于分析共轭聚合物构象变化及其对能量转移过程的影响.     

线极化Bell-Bloom测磁系统中抽运光对磁场灵敏度的影响

利用适用于线极化Bell-Bloom测磁系统的布洛赫方程和含有自旋弛豫的速率方程,以铯原子为研究对象,分析了抽运光对磁场灵敏度的影响,并在实验上分别采用与铯原子D1线和D2线共振的线偏光作为抽运光和探测光,用充有缓冲气体的气室进行了实验.实验结果与理论分析一致,均表明只有在一定的光强范围内,增大抽运光光强可以提高磁场灵敏度.且利用这一方法分析了原子的自旋弛豫对磁场灵敏度的影响.这项研究对于深入认识线极化的Bell-Bloom测磁系统,以及如何通过优化系统实现磁场灵敏度的提高具有重要的意义.