A novel scheme for guiding arbitrary buffer-gas cooled neutral molecules in a hollow optical fiber(HOF) using a red-detuned HE 11 mode is proposed and analysed theoretically.We give the electromagnetic field distribution of the HE 11 mode in the HOF and calculate the optical potential of an I 2 molecule,and study the molecule guiding mechanism using a classical Monte Carlo simulation.Using a 6 kW input laser,an S-shape HOF with a 2 cm curvature radius for both bends,and an input molecular beam with a transverse temperature of 0.5 K and longitudinal temperature of 5 K,we obtain a guiding efficiency of ～0.126% for the scheme,and the transverse and longitudinal temperatures of the guided molecular beam are 1.9 mK and 0.5 K,respectively.
为了研究Yb^(3+):LuLiF_4晶体在反Stokes荧光制冷过程中的热负载管理机制,开展了在常压(1.0×105Pa)和高真空(2.5×10-3 Pa)状态下的激光制冷实验。掺杂浓度为5 mol%的样品由两根光纤支撑,被放置在真空状态不同的腔体内。利用波长1 020 nm,功率3 W的激光激发样品。在常压下,样品温度相对室温下降了△T≈12 K;在高真空下,△T≈26 K。对于常压状态,空气热对流负载约11.23 m W,光纤热传导负载约0.03 m W,腔体热辐射负载约4.8 m W。对于高真空状态,空气热对流负载约0.03 m W,光纤热传导负载约0.07 m W,腔体热辐射负载约10.4 m W。实验结果表明,当腔体压强由-105 Pa降至-10-3Pa时,空气热对流负载几乎忽略不计,而腔体热辐射负载则成为作用在制冷样品上最主要的热负载。
Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical^(138)Ba^(19) F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck–Condon factors between the X^2Σ^+_(1/2)and A^2Π_(1/2) states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hyperfine structure of the X^2Σ^+_(1/2)state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper(A^2Π_(1/2)) and lower(X^2Σ^+_(1/2)) levels are also studied, and their respective g factors are obtained under a weak magnetic field.Its large g factor of the upper state A^2Π_(1/2) is advantageous for magneto-optical trapping. Finally, by studying Stark effect of Ba F in the X^2Σ^+_(1/2), we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled Ba F is also a promising candidate for precision measurement of electron electric dipole moment.
We propose a controllable high-efficiency electrostatic surface trap for cold polar molecules on a chip by using two insulator-embedded charged rings and a grounded conductor plate. We calculate Stark energy structure pattern of ND3 molecules in an external electric field using the method of matrix diagonalization. We analyze how the voltages that are applied to the ring electrodes affect the depth of the efficient well and the controllability of the distance between the trap center and the surface of the chip. To obtain a better understanding, we simulate the dynamical loading and trapping processes of ND3 molecules in a |J, KM = |1,-1 state by using classical Monte–Carlo method. Our study shows that the loading efficiency of our trap can reach ～ 88%. Finally, we study the adiabatic cooling of cold molecules in our surface trap by linearly lowering the potential-well depth(i.e., lowering the trapping voltage), and find that the temperature of the trapped ND3 molecules can be adiabatically cooled from 34.5 m K to ～ 5.8 m K when the trapping voltage is reduced from-35 k V to-3 k V.
An electrostatic trap for polar molecules is proposed. Loading and trapping of polar molecules can be realized by applying different voltages to the two electrodes of the trap. For ND3 molecular beams centered at ～10 m/s, a high loading efficiency of ～67% can be obtained, as confirmed by our Monte Carlo simulations. The volume of our trap is as large as ～3.6 cm3, suitable for study of the adiabatic cooling of trapped molecules. Our simulations indicate that trapped ND3 molecules can be cooled from ～23.3 m K to 1.47 m K by reducing the trapping voltages on the electrodes from 50.0 k V to1.00 k V.
