Dynamic control of retrieval contrast in a Λ-type atomic system

We propose an efficient scheme for optimizing the optical memory of a sequence of signal light pulses in a system of ultracold atoms in Λ configuration. The memory procedure consists of write-in, storage, and retrieval phases. By applying a weak microwave field in the storage stage, additional phase-dependent terms are included, and the contrast of the output signal pulses can be dynamically controlled (enhanced or suppressed) through manipulating the relative phase φ between optical and microwave fields. Our numerical analysis shows that the contrast is enhanced to the most extent when φ=1.5π. In addition, the contrast is in proportion to the Rabi frequency of the microwave field with a certain relative phase.     

Dynamic control of retrieval contrast in a ∧-type atomic system

We propose an efficient scheme for optimizing the optical memory of a sequence of signal light pulses in a system of ultracold atoms in ∧ configuration.The memory procedure consists of write-in,storage,and retrieval phases.By applying a weak microwave field in the storage stage,additional phase-dependent terms are included,and the contrast of the output signal pulses can be dynamically controlled（enhanced or suppressed） through manipulating the relative phase φ between optical and microwave fields.Our numerical analysis shows that the contrast is enhanced to the most extent when φ = 1.5π.In addition,the contrast is in proportion to the Rabi frequency of the microwave field with a certain relative phase.     

Co—Mo／Al2O3型重整预加氢催化剂的研制

考察了不同方法制备的Ｃｏ－Ｍｏ／Ａｌ２Ｏ３型重整预加氢催化剂对石油加氢脱硫活性的影响，选出了一种工业生产步骤简单，金属含量容易控制，并且不腐蚀设备的碱必等量共浸法制备的ＤＳ－９４８催化剂。该催化剂在温度３５０℃，压力３．０ＭＰａ，液体空速６．０ｈ＾－１，体积氢油比７０的条件下，满足了双金属重整催化剂对精制石油脑油杂质含量的要求。     

冷铷原子样品中高效静态光信号的生成与调制

为了提高光信息处理元件的性能,实现高效率光信号的静止与存储,本文建立了由双向耦合场耦合的冷铷（87Rb）原子的四能级双Λ型能级机制,并对此机制在生成静态光信号时要求的高效性、持续时间,控制耦合场所需的操作条件以及对信号场强度的相位调制等进行了研究。首先,选取四能级双Λ型87Rb冷原子精细能级,用一对反向传播的行波激光场对能级进行近共振耦合,并沿耦合场方向输入一个正向弱光信号进行探测。接着,通过适当的绝热开启、关闭耦合场,存储光信号和生成高保真度静态光信号。然后,通过选取87Rb原子的不同精细能级结构,得出实现静态光所需满足的必要条件。最后,采用相位调制法对光信号进行处理。结果表明：生成的静态光信号具有高效性,过程持续时间约为80μs;相位调制法可以周期调节静态光脉冲的强度。在此机制下生成的静态光信号满足高效性、易于全光调节和长时效性等要求。     

Experiments on trapping ytterbium atoms in optical lattices

Experiments on trapping ytterbium atoms in various optical lattices are presented. After the two-stage cooling, first in a blue magneto-optical trap and then in a green magneto-optical trap, the ultracold 171 Yb atoms are successfully loaded into one-, two-, and three-dimensional optical lattices operating at the Stark-free wavelength, respectively. The temperature, number, and lifetime of cold 171 Yb atoms in one-dimensional lattice are measured. After optimization, the one-dimensional lattice with cold 171Yb atoms is used for developing an ytterbium optical clock.     

Development of adjustable permanent magnet Zeeman slowers for optical lattice clocks

We develop a permanent-magnet Zeeman slower with adjustable magnets along the longitudinal and radial directions.Produced by four arrays of cylindrical magnets, the longitudinal magnetic field in the slower is tunable if relevant parameters vary, for example, laser detuning or intensity. The proposed Zeeman slower can be reconfigured for Sr atoms. Additionally,we demonstrate that the residual magnetic field produced by the permanent magnets in the magneto-optical trap region can be as small as 0.5 Gs.     

贵金属催化剂用于重整后加氢

研制了一种以铂为主的担载型重整后加氢催化剂。与目前工业上使用的Co-Mo-Al 型催化剂相比,上述铂催化剂具有使用温度低(135—165℃),空速高(14h~(-1))的特点。在145℃的低温下反应,加氢产品溴价为0.003,比工业产品规格(<0.07)低一个数量级。该催化剂选择性好,在较宽温度范围内基本没有芳烃加氢损失。连续运转3000小时活性未见下降,表示催化剂稳定性好。此外还考察了催化剂的再生性能和原料中氯含量对加氢反应的影响。     

甲醇-水溶剂中菲和蒽的光化学特性研究

以高效液相色谱(HPLC)、气相色谱-质谱(GC/MS)分析了甲醇-水溶剂中菲、蒽在漫反射光和固定紫外波长光照射下的浓度变化和产物;引入芬顿(Fenton)反应研究了菲、蒽的光降解行为和引发机理。菲的光化学产物主要是1,1′-二苯基-2,2′-二甲醛、菲酚、邻苯二甲酸二甲酯和2,6-二叔丁基酚;蒽的光解产物仅为蒽醌。结果表明,光照激发菲、蒽的π-π*电子跃迁是引发光降解的关键步骤,其光解速率与菲、蒽在紫外光区(λ<300nm)的吸光度有关。     

Clock-transition spectrum of ^171yb atoms in a one-dimensional optical lattice

An optical atomic clock with 171Yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb-Dicke regime. Furthermore, these cold 171Yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0-3P0 clock-transition spectrum of these 171Yb atoms is obtained by measuring the dependence of the population of the ground-state 1S0 upon the clock-laser detuning.