Time-dependent analysis of tunneling effect in the formation of ultracold molecules via photoassociation of laser-cooled atoms

The paper contains a time-dependent investigation of the tunneling effect observed in the photoassociation spectrum of Cs₂ and attributed to the 0_g ^-(6s, 6p _3/2) double well. When by photoassociation of two cold cesium atoms a vibrational level of the outer well is populated, tunneling is an efficient mechanism for transferring the population to the inner well (R < 15a ₀), where spontaneous emission may lead to formation of cold molecules in low vibrational levels of the a ³Σ⁺ _u(6s, 6s) electronic state. This tunneling effect is analyzed by wavepackets propagation, first considering the double well potential alone, and following a packet made by a superposition of states initially located at large distances. Characteristic times for the vibration dynamics, corresponding to a beating phenomenon between the two wells, to partial “revival” at large distances, and to maxima in the population localized in the inner well are reported and discussed. Second, we simulate the two-channels a ³Σ⁺ _u(6s, 6s)↦0_g ^-(6s, 6p _3/2) photoassociation at detunings around 2.9 cm^-1: the inner well can be populated either by the excitation of a vibrational level of the external well (resonant excitation), or by tuning the photoassociation laser at the energy of the inner well level which displays tunneling (“off-resonance excitation”). In the first case the photoassociation is efficient, while the tunneling probability is small; in the second, the tunneling probability is large, so that despite the poor efficiency of the photoassociation process, more population can be transferred to the inner well. This second choice is shown to be very sensitive to the laser intensity, which could be used to control the population of the inner well and hence the formation of ultracold molecules in low vibrational levels. Received 19 April 2002 Published online 1st October 2002 RID="a" ID="a"e-mail: francoise.masnou@lac.u-psud.fr     

Line shape analysis of two-colour photoassociation spectra on the example of the Cs ground state

Two-photon photoassociation spectra in a Λ-type excitation scheme are analysed under the systematically varied experimental conditions of frequency detunings and laser intensities. Line shape fits are presented as well as the investigation of intensity and detuning dependent line shifts. From both we determine the attained spectroscopic precision, that is corrected for a systematic line shift due to the thermal distribution of atoms in the trap. An energy correction for this effect is given. Information about the feasibility of generating translationally cold molecules in a well defined rotational and vibrational level by the photoassociation process is derived from the analysis. Received 21 May 2002 Published online 15 October 2002 RID="a" ID="a"Current address e-mail: christian.lisdat@ptb.de RID="b" ID="b"e-mail: pierre.pillet@lac.u-psud.fr     

激光冷却和捕陷中性原子③

6 激光冷却和捕陷中性原子技术的应用 前面已经提到,激光冷却和捕获中性原子技术最主要的应用是在精密计量和超冷原子物理两个方面.在精密计量方面最为典型的是可用于原子频标的"原子喷泉"(atomic fountain)技术;而在超冷原子物理方面最为典型的是玻色-爱因斯坦凝聚(Bose-Einstein condensation)和原子波激射器(atom laser)的实现.     

Bright optical lattices in a longitudinal magnetic field. Experimental study of the oscillating and jumping regimes

All the bright optical lattices studied so far have been designed to obtain a circularly polarized light at the bottom of the optical potential wells. This condition minimizes the departure rate of the atoms from the fundamental adiabatic surface and permits an oscillating regime in a large range of parameters. We present here an experimental study of cesium atoms in a three-dimensional optical lattice, where the light is linearly polarized at the bottom of the potential wells. Temperature measurements and pump-probe spectroscopy give similar results for this lattice and for the conventional lin lin lattice (which have circular polarizations at the bottom of the wells) despite the fact that one lattice operates in the jumping regime and the other in the oscillating regime. We study the behaviour of the two types of lattices in a longitudinal magnetic field, with particular emphasis on the zero field and strong field regimes. The strong field situation is very simple because the eigenstates are then almost pure Zeeman substates and the adiabatic and diabatic potential surfaces are identical. The comparison between the zero-field and the high-field situations shows that the diabatic potentials are more appropriate to account for experimental observations in the novel lattice. Received: 9 October 1997 / Accepted: 6 November 1997     

TEM01模式激光对两能级原子的作用力研究

推导了两能级原子在稳态和小速度一阶微扰近似下的受力矢量方程，并分析表明ＴＥＭ０１模光场以原子的作用力中存在旋涡力，对在大正失谐δ〉〉Ω０〉〉Г和ｚ〈〈ｚ０＝ｋｗ＾２／λ条件下的ＴＥＭ０１模行波和驻波场中原子的受力进行了分析，对行波场，自发辐射对原子运动的影响很大，但在ｒ〈〈λ区域内原子受到横向囚禁力；对驻波场，自发辐射的影响可以忽略，考虑在ｚ方向波长范围内原子的平均受力得到的结论为：在横向，除了有     

HIRFL-CSRm纵向随机冷却-槽形滤波冷却模拟研究

 通过Fokker Planck方程,对拟在HIRFL-CSRm上建造的纵向槽形滤波器（notch filter）的冷却机理进行了研究,得出了冷却原理及冷却时间的表达式,并对影响冷却时间和冷却效果的因素进行了模拟和讨论,模拟结果表明,噪信比越小,冷却时间越短,冷却效果越好;带宽越宽冷却越快。该研究为具体纵向冷却系统的设计和优化提供了依据。     

Magneto-optical trapping of Stark-slowed metastable He atoms

We report on the first successful loading of a magneto-optical trap (MOT) with metastable He atoms from a Stark-slower. Thereby, deceleration of the atoms relies on laser-atom interaction in an inhomogeneous electric field. We show that the results obtained are comparable with early results from other groups achieved with a Zeeman slower. The Stark slower, which is able to fully control the final velocity of the atomic He beam, is the first step in achieving complete spin independent kinematic control based solely on electric fields. Received 2 October 2002 / Received in final form 20 January 2003 Published online 29 April 2003 RID="a" ID="a"e-mail: eichmann@mbi-berlin.de     

40J激光装置研制

 报道了一台输出能量在40J量级的激光装置。该装置从星光Ⅱ激光装置分光作为光源,由放大器链、能源系统和支撑桁架等三大部分构成。对整个激光装置的模拟计算结果表明：装置的增益能力足够输出40J,B积分满足ΔB小于1.8的要求。研制了一种全腔水冷新型放大器,对其小信号增益系数和增益均匀性进行了测量,实验得出增益系数β为0.034cm ^-1,增益均匀性为91.84%。结果表明这种放大器完全能满足此激光装置的设计要求。     

固体材料反斯托克斯荧光制冷的理论研究及其最新进展

本文首先回顾了反斯托克斯荧光制冷的历史发展,简单讨论了激光制冷的循环过程及其制冷条件;其次,概述了反斯托克斯Raman散射、反斯托克斯荧光制冷的热力学理论和热力学限制,重点介绍了适用于各种制冷材料(如稀土离子掺杂玻璃、半导体和晶体等)反斯托克斯荧光制冷研究的理论模型,并简单讨论了激光制冷实验中各种测量温度变化的实验方法及其基本原理。最后,就反斯托克斯荧光制冷的一种最新应用及其前景进行了简单介绍与展望。