A versatile electrostatic trap with open optical access

A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking ND₃ molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 mK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.     

Absolute density measurement of nitrogen dioxide with cavity-enhanced laser-induced fluorescence

The absolute number density of nitrogen dioxide(NO_2) seeded in argon is measured with cavity-enhanced laserinduced fluorescence(CELIF) through using a pulsed laser beam for the first time. The cavity ring down(CRD) signal is acquired simultaneously and used for normalizing the LIF signal and determining the relationship between the measured CELIF signal and the NO_2 number density. The minimum detectable NO_2 density down to(3.6±0.1)10~8 cm~(-3) is measured in 60 s of acquisition time by the CELIF method. The minimum absorption coefficient is measured to be(2.0±0.1)10~(-9) cm~(-1), corresponding to a noise equivalent absorption sensitivity of(2.2±0.1)10~(9) cm.~(-1)Hz~(-1/2). The experimental system demonstrated here can be further improved in its sensitivity and used for environmental monitoring of outdoor NO_2 pollution.     

Matter-wave interference in an axial triple-well optical dipole trap

This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by ～37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth ～0.5 μK and volume ～74 μm³ are suitable to trap and manipulate an atomic Bose--Einstein condensation (BEC). Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.     

一种新颖的实现冷原子或冷分子囚禁的可控制光学四阱及其二维光学晶格

原子光学晶格为精确操控中性原子和研究某些基本物理问题提供了一种方法。提出了一种利用单光束照明余弦型振幅光栅与透镜组合系统实现冷原子或冷分子囚禁的可控制光学四阱新方案,计算了四阱的光强分布,讨论了从光学四阱到双阱或单阱的演化过程,并导出了光学四阱的几何参量、光强分布、强度梯度及其曲率与光学透镜系统参量间的解析关系,获得了四阱间距与光栅空间频率的关系。研究表明通过改变余弦光栅的空间频率即可实现从光学四阱到双阱或单阱的连续双向演化。     

A New Desirable Molecular Species for Stark Deceleration

We demonstrate a new molecular sample （CH radical） for Stark deceleration by Monte Carlo simulation, study the dependences of the decelerating effect on the different phase angles, stage number and decelerating voltages, and obtain some new optimized conditions and parameters. We also calculate the Stark energy shift of different quantum states of CH radical in the Stark decelerator electrostatic field and their populations in a supersonic CH molecular beam. Our study shows that the mean velocity of the supersonic CH molecular beam in the 2^∏1/2 state can be decelerated from 380 m/s to 24 m/s, and the corresponding translation temperature is lowered from 2.8 K to 27mK. It is thus clear that the CH radical is a new and desirable candidate for Stark deceleration.     

不同滑滚比下润滑油膜流变特性试验观察与数值模拟

通过在原有的球-盘接触光干涉润滑油膜测量装置上增设摩擦力测量单元,实现了任意滑滚比下油膜厚度和摩擦系数的同步测量与润滑状态的直观识别. 采用FVA3参考油,分析了不同滑滚比、速度和载荷下的摩擦系数变化规律,并结合油膜干涉图明确了润滑状态与热效应机制,推断出摩擦系数曲面在较低速工况存在混合润滑区域;通过采用基于恢复时间的流变模型对FVA3油品的流变润滑进行数值模拟,并与同等工况下的试验结果进行定量对比,两者取得了良好的吻合性,验证了试验测量的准确性和流变模型的适用性.      

重力光学势阱中消逝波冷却原子的蒙特卡罗研究

讨论了三能级原子在消逝波光场作用下的Ｓｉｓｙｐｈｕｓ冷却和几何冷却机制,通过蒙特卡罗（Ｍｏｎｔｅ－Ｃａｒｌｏ）方程分别模拟了消逝波光场在方锥形势阱和圆锥阱两种情况下对原子冷却的动力学过程,并计算了原子在不同的失谐量、激光功率及消逝波的判断宽度下的冷却情况。结果表明,增大消逝波的激光功率能有效地减少原子的损耗,但对冷却结果影响不大;而消逝波的判断宽度不够宽时,结果偏差较大;对于方锥形势阱,失谐量趣小     

氮原子同位素计算

本文利用多组态Dirac-Hartree-Fock和相对论组态相互作用的方法计算了氮原子的同位素¹⁴N和¹⁵N的四对能级跃迁：3s⁴P→3p⁴P°,3s⁴P→3p⁴D°,3s²D→5p²D°,和3s²P→3p²P°相应的特殊质量位移系数和场因子. 由计算所得的正常质量位移,特殊质量位移系数和场因子获得了氮原子同位素的正常质量位移、特殊质量位移和场位移. 同时将计算结果和报道的实验和理论计算结果进行了比较.     

π相位板产生矢量光束的高数值孔径聚焦特性研究

借助马赫曾德尔干涉仪光路,用简单的π相位板把线偏振光转换为径向和角向矢量空心光束,应用RichardsWolf经典矢量衍射模型,计算了高数值孔径透镜聚焦条件下光波电磁场的分布,结果表明:用10-3 W量级的激光功率照明,产生轴对称矢量空心光束的最大光强达到1011 W·m-2量级,最大光强梯度达到1017 W·m-3量级,暗斑半径仅有0.24λ,同时出现了很强的纵向电场和磁场分布;调节干涉仪光路的光程差可调节局域光子轨道角动量密度的分布,这种光束在原子光学中有很好的应用前景。     

用卢瑟福背散射和弹性背散射分析高Tc超导薄膜中的元素组份及氧含量

提出了用能量为１．５－２．５ＭｅＶ的质子弹性背散射分析（ｅｌａｓｔｉｃ ｂａｃｋｓｃａｔｔｅｒｉｎｇ，缩写为ＥＢＳ）来测定薄膜中的氧含量，这个方法对于厚度为几十纳米到几个微米的样品，测量精度约５％。采用ＲＢＳ分析并结合ＥＢＳ分析，可全面测得薄膜中各元素的含量。 关键词：