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

Abstract

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 mK. 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.

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

“…Compared with the disk electrostatic trap (DET) in Ref. [27], the ODET and TDET proposed here achieve a significant improvement in the trap loading efficiency. Using MgF as the target molecule, the dependences of the trap load-043701-6 ing efficiencies of DET, ODET, and TDET on the incident velocity of the slow beam under the single loading operation mode are calculated, respectively, as shown in Fig.…”

“…Applying the same voltages on the electrodes of DET as those used in Ref. [27], i.e., voltages of 30 kV and 50 kV to the first and second disk electrodes in the loading configuration and voltages of 50 kV and 50 kV in the trapping configuration, a highest loading efficiency of 25.8% is obtained with an incident velocity of 6 m/s. Meanwhile, applying voltages of U = 26 kV to ODET (or TDET), a highest loading efficiency of 78.4% (or 81.6% ) is achieved with an incident velocity of 10 m/s (or 11 m/s), resulting in an increase by a factor of two in the number of the trapped molecules.…”

“…A variety of techniques have been developed to trap cold molecules. [17][18][19][20][21][22][23][24][25][26][27] In 1998, Doyle group realized magnetic trapping of calcium monohydride molecules thermalized in helium buffer gas. [28] In the same year, Knize group successfully trapped cesium dimers with an optical trap.…”

Collision of cold CaF molecules: Towards evaporative cooling

“…The simulation of the evaporative cooling followed the model developed in the group of Ketterle. [29,30] When the trapping potential decreases from U(k B T ) to U (ηk B T ), the molecular number N, the trapping volume V , the molecular temperature T , and the molecular density n change to N , V , T , and n , respectively. The relations are as follows: [29,30]…”

Production of cold CN molecules by photodissociating ICN precursors in brute-force field

“…[6][7][8][9] Continuing efforts in search of new methods for the production of cold atoms and molecules have never ceased. [10][11][12][13][14][15][16][17] In 2007, Matthews et al [18] proposed that cold oxygen atoms could be made with zero mean velocity in the laboratory frame by photodissociating NO 2 molecules.…”