Improvement of modified analytic embedded atom method potentials for noble metals and Cu

The modified analytic embedded atom model (EAM) potentials considering farther neighbor atoms are improved for the noble metals (Ag, Au, Pt, Pd, Rh) and Cu. We not only adopt an end processing function and an enhanced smooth continuous condition for the pair potential, but also adjust the model parameters of multi-body potential by fitting a cohesive energy, a mono-vacancy formation energy, the Rose equation curve for the cohesive energy as a function of lattice parameter, a structure energy difference, elastic parameters and an equilibrium condition of crystal. The calculation results of structure energy differences misfit the experiment data for the noble metals and Cu in the unimproved EAM, because anyone of these differences have not been considered in the calculation of its model parameters. After the modification, the model showed better simulation results for the noble metals and Cu.     

Observation of magnetization step at order–disorder transition in MgB2 single crystals

We have studied the order–disorder transition in high quality MgB₂ single crystals, using a torque magnetometry combined with a ‘vortex shaking’ technique. In the wide range of temperature T, field H and the H direction, we succeed in obtaining reversible magnetization curves M_rev(T, H) by shaking the pinned vortices. Especially at low temperatures below 25 K and high fields, where the irreversible magnetization curve exhibits the peak effect due to the order–disorder transition, it is found that the peak is transformed into the clear step in M_rev(H). Similar step-like behavior is also observed in the temperature dependence of magnetization M_rev(T). These results give direct evidence that the order–disorder transition, which is hidden by the large hysteresis of magnetization, has the nature of first-order transition.     

法拉第旋转镜用于补偿单光子偏振漂移的实验研究

研究了法拉第旋转镜用于补偿单模光纤中1 550 nm单光子传输的偏振漂移特性.比较了不同平均光子数下经由不同长度单模光纤传输后单光子偏振漂移的差异,以及使用法拉第旋转镜的偏振漂移抑制比.实验结果表明,在50 km光纤50 kcps光子计数（光强）下偏振漂移改善最优,偏振漂移抑制比达25.3.     

电场中Eu原子电离阈移动的实验研究

提出了一种新方法, 精确确定了稀土Eu原子第一电离阈的位置. 先用脉冲电场对Eu原子的高激发Rydberg态进行延时场电离探测, 再通过反向静电场排除光电离和自电离等其他路径所产生的离子信号的干扰, 观察并研究了Eu原子第一电离阈随着电场移动的规律. 由此所确定的零场下第一电离阈的数值与采用其他方法所确定的文献值^{[1, 2]}相一致, 从而验证了该方法的可靠性.     

液体空分流程形式浅析

通过对全液体空分装置不同流程组织形式进行分析和模拟计算、能耗与投资的比较,根据不同规格的产品要求,进行合适的流程形式选择,以可达到节能降耗的目的。     

高频原子波导中冷原子的磁导引

建立了高频原子波导模型,分析了铷冷原子在该波导内与磁场的相互作用势。高频波导线圈输入电流,在线圈中心轴线区域的势阱深度为mK量级,在线圈的径向能对温度为100 K左右的冷原子实现囚禁。通过分析可知改变输入波导线圈的输入电流大小,可改变势场的大小。计算了进入高频原子波导的冷原子和波导磁场产生相互作用束缚力的大小。在波导轴线中心区域,原子受到的束缚力较大,最大为1.710－23 N,为原子所受重力的10倍。     

利用自电离探测技术研究Sm原子Rydberg态光谱

采用孤立实激发与自电离探测技术相结合的方法对Sm原子偶宇称高激发态进行了系统研究.按照不同的自电离通道将所测数据进行了分类和比较,并进行了详细讨论.不仅报道了许多收敛于不同电离限的Rydberg态的能级位置和跃迁的相对强度等信息,而且还把处于同一能域内的Rydberg态和价态进行了辨识.另外,不但提供了一种有效识别不同类型的高激发态的鉴别技术,而且还对处于41800 cm^-1到43800 cm^-1能域内的Rydberg态和价态的光谱特性进行了详细分析和讨论. 关键词： 自电离探测 Rydberg态 Sm原子     

Nonlinear Effects in Quantum Dynamics of Atom Laser: Mean-Field Approach

Quantum dynamics and statistics of an atom laser with nonlinear binary interactions are investigated in the framework of mean-field approximation. The linearized effective Hamiltonian of the system is accurately solvable. It is shown that, although the input radio frequency field is in an ordinary Glauber coherent state, the output matter wave will periodically exhibit quadrature squeezing effects purely originated from the nonlinear atom-atom collisions.     

Electromagnetically—induced transparency in a multi—V—type system in cesium atomic vapour

Electromagnetically-induced transparency is observed in a three-level multi-V-type system in cesium vapour at room temperature.The absorption property is measured and the hyperfine structures of atomic states can be datermined.The results of the experiment agree with the theoretical analysis.     

Cs 39D态Rydberg原子Stark光谱的实验研究

本文从理论和实验上对Cs39D态Rydberg原子在弱电场作用下的Stark效应做了详细研究. 理论上利用数值方法计算了Cs原子39D态的Stark结构;实验上,采用两步激发超冷基态原子获得超冷Rydberg原子,通过场电离的方法获得了39D态的Stark光谱,测量获得α^5/2₂,α^5/2₀,α^3/2₂和α^3/2₀相应的极化率分别为：62(7),－146(13), 73(6) 和－106(20) MHz·V^-2cm²,实验结果与理论相符合.