Loading Stark-decelerated molecules into electrostatic quadrupole traps

Beams of neutral polar molecules in a low-field seeking quantum state can be slowed down using a Stark decelerator, and can subsequently be loaded and confined in electrostatic quadrupole traps. The efficiency of the trap loading process is determined by the ability to couple the decelerated packet of molecules into the trap without loss of molecules and without heating. We discuss the inherent difficulties to obtain ideal trap loading, and describe and compare different trap loading strategies. A new “split-endcap” quadrupole trap design is presented that enables improved trap loading efficiencies. This is experimentally verified by comparing the trapping of OH radicals using the conventional and the new quadrupole trap designs.     

Stark-potential evaporative cooling of polar molecules in a novel optical-access opened electrostatic trap

We propose a novel optical-access opened electrostatic trap to study the Stark-potential evaporative cooling of polar molecules by using two charged disk electrodes with a central hole of radius r0= 1.5 mm, and derive a set of new analytical equations to calculate the spatial distributions of the electrostatic field in the above charged-disk layout. Afterwards, we calculate the electric-field distributions of our electrostatic trap and the Stark potential for cold ND3 molecules, and analyze the dependences of both the electric field and the Stark potential on the geometric parameters of our charged-disk scheme,and find an optimal condition to form a desirable trap with the same trap depth in the x, y, and z directions. Also, we propose a desirable scheme to realize an efficient loading of cold polar molecules in the weak-field-seeking states, and investigate the dependences of the loading efficiency on both the initial forward velocity of the incident molecular beam and the loading time by Monte Carlo simulations. Our study shows that the maximal loading efficiency of our trap scheme can reach about 95%, and the corresponding temperature of the trapped cold molecules is about 28.8 m K. Finally, we study the Stark-potential evaporative cooling for cold polar molecules in our trap by the Monte Carlo method, and find that our simulated evaporative cooling results are consistent with our developed analytical model based on trapping-potential evaporative cooling.     

一种实现冷分子囚禁的可控制静电双阱方案

提出了采用双环形载荷导线和两透明电极系统实现冷分子静电囚禁的可控制静电双阱的新方案,计算了带电圆导线和带电板所产生的静电场分布,从几个方面分析了这个囚禁方案的优点. 提出了一种有效的冷分子装载方法,并研究了双阱到单阱的演化过程. 研究表明,该可控制静电双阱方案不仅方便装载与操控弱场搜寻态的极性冷分子,而且在分子物质波的干涉、纠缠、冷碰撞,甚至进行双阱分子BEC研究等分子光学领域中有着广阔的应用前景. 关键词： 极性冷分子 静电囚禁 可控制静电双阱 分子光学     

Novel electrostatic trap for cold polar molecules

We propose a novel scheme in which cold polar molecules are trapped by an electrostatic field generated by the combination of a pair of parallel transparent electrodes (i.e., two infinite transparent plates) and a ring electrode (i.e., a ring wire). The spatial distributions of the electrostatic fields from the above charged wire and the charged plates and the corresponding Stark potentials for cold CO molecules are calculated; the dependences of the trap centre position on the geometric parameters of the electrode are analysed. We also discuss the loading process of cold molecules from a cold molecular beam into our trap. This study shows that the proposed scheme is not only simple and convenient to trap, manipulate and control cold polar molecules in weak-field-seeking states, but also provides an opportunity to study cold collisions and collective quantum effects in a variety of cold molecular systems, etc.     

芯片表面的冷极性分子静电阱与微阱阵列

提出一种利用三根载荷金属杆来实现在芯片表面陷俘冷极性分子的静电阱.给出空间静电场等高线分布.通过调节电极电压操控阱中心距离芯片表面的高度.用经典的蒙特卡罗方法模拟冷分子被装载和囚禁的动力学过程.方案对中心速度为11 m·s^-1的冷分子束,最大装载效率可以达到40%,阱中分子的温度大约为25 mK.方案可以进一步微型化、集成化,形成一维和二维静电微阱阵列,在量子计算、低维物理等方面有应用价值.     

一种针对弱场搜寻态冷极性分子的可控静电表面囚禁方案

提出一种使用带电金属环和六个球电极和一个外加偏置电场实现对冷极性分子静电囚禁的新方案.计算装载和囚禁时空间电场分布.囚禁中心距离芯片表面的高度可以通过外电场和环形电极所加电压来操控.蒙特卡罗模拟表明对于中心速度为15 m·s^-1的ND₃分子束,装载效率可以达到70%,得到冷分子的温度大约为45 mK.当继续增加偏置电场强度时,单阱分裂为对称的两个阱.如果同时改变球形电极上所加电压,得到不对称的两个阱,可以借此来调节两个阱中所囚禁的冷分子数目的比例.为了易于理解,用蒙特卡罗方法模拟了装载、囚禁、分裂冷分子波包的动力学过程.     

Two types of highly efficient electrostatic traps for single loading or multi-loading of polar molecules

Two novel electrostatic traps named octopole-based disk electrostatic trap(ODET)and tubular-based disk electrostatic trap(TDET)are proposed for trapping cold polar molecules in low-field-seeking states.Using MgF as the target molecule,single loading and multi-loading methods are numerically simulated with varied incident velocities of slow molecular beams in the two types of traps,respectively.In ODET,with an incident velocity of 10 m/s,a highest loading efficiency of 78.4% or 99.9% has been achieved under the single loading or multi-loading operation mode.In TDET,with an incident velocity of 11 m/s,a highest loading efficiency of 81.6% or 106.5% has been achieved using the two loading methods,respectively.With such high loading efficiencies,the trapped cold molecules can be applied in the researches of cold collisions,high precision spectroscopy,and precision measurements.Especially,together with a blue-detuned hollow beam,the new electrostatic traps proposed here offer a new platform for the following gradient-intensity cooling of MgF molecules,which may provide a new way to produce high density ultracold molecules.     

可操控二种冷原子或冷分子样品的光学双阱新方案及其实验研究

提出了一种构建可囚禁与操控二种冷原子或冷分子样品的光学双阱的新方案,该方案采用常用的液晶空间光调制器作为分光器件,分光调制函数类似二元相位光栅;对提出的方案进行了模拟实验研究,并研究了从光学双阱到单阱的双向演化过程,该光学双阱的模拟实验结果表明与理论方案相符,双阱的操控性好,有利于二种不同的冷原子或冷分子样品的装载与操控等相关实验研究. 关键词： 原子光学 原子分子囚禁 液晶空间光相位调制器 光学双阱     

A spatial electrostatic beam splitter for polar molecules in weak-field-seeking states

A spatial electrostatic beam splitter composed of six charged poles for polar molecules in weak-field-seeking states is proposed. First, the schematic diagram is given. With the help of finite element software the spatial distribution of the electrical field is calculated. The dynamic process of the loading and splitting polar molecules is simulated using the classical Monte Carlo method. The influences of the longitudinal velocity of the incident molecular beam and the voltages on the loading efficiency are studied. Two output arms of the beam splitter can be cut off at a certain position to adjust the splitting ratio of the molecular beam. Then the influences of the voltages and cutting positions on the splitting ratio are investigated. The results indicate that the splitting ratio can be manipulated conveniently from 0% to 100%.     

Theoretical derivation and simulation of a versatile electrostatic trap for cold polar molecules

We propose a versatile electrostatic trap scheme using several charged spherical electrodes and a bias electric held.We hrst give the two-ball scheme and derive the analytical solution of the electric held.In order to make a comparison,we also give the numerical solution calculated by the hnite element software(Ansoft Maxwell).Considering the loading of cold polar molecules into the trap,we give the three-ball scheme.We hrst give the analytical and numerical solutions of the distribution of the electric held.Then we simulate the dynamic process of the loading and trapping cold molecules using the classical Monte Carlo method.We analyze the influence of the velocity of the incident molecular beam and the loading time on the loading efficiency.After that,we give the temperature of the trapped cold molecules.Our study shows that the loading efficiency can reach 82%,and the corresponding temperature of the trapped molecules is about 24.6 mK.At last,we show that the single well divides into two ones by increasing the bias electric held or decreasing the voltages applied to the spherical electrodes.