超低频调制光缔合光谱的实验研究

通过激光冷却技术在磁光阱中俘获原子数约107,温度约200 μK,直径约400 μm的超冷铯原子,利用超冷铯原子光缔合方法制备了激发态的超冷铯分子。实验研究了光缔合光不同扫描速率对铯分子振转光谱分辨率的影响,发现光缔合光扫描速率较慢时,铯分子振转光谱分辨率较高。通过高灵敏的雪崩光电探测器探测冷原子荧光,获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0-_g长程态高分辨振转光谱。为了实现受控拉曼光缔合制备超冷基态分子,光缔合激光频率需要锁定在原子-分子共振跃迁线,对超冷原子光缔合光谱进行了超低频波长调制,通过改变调制幅度和调制频率获得最优化的一阶微分信号,将该信号反馈回激光器,实现闭合环路稳频,满足了受控拉曼光缔合制备振转能级可控的基态分子的实验要求,该工作对研究受限空间中的超冷原子分子具有很重要的意义。     

超冷铯分子0g-长程态的振转光谱研究

通过超冷铯原子光缔合制备激发态的超冷铯分子. 利用冷原子荧光频率调制技术获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0_g^-长程态高分辨振转光谱, 计算得到0_g^- 长程态振动量子数从0到51的不同振动能级的转动常数, 和Daniel研究小组的理论结果符合得很好. 关键词： 超冷铯分子 光缔合 振转光谱     

最优化参数控制提高超冷铯分子振转光谱的信噪比

超冷原子光缔合光谱对于研究长程分子势能结构、分子常数和分子相关动力学过程具有重要意义.光缔合光谱的信噪比作为衡量探测技术的重要指标之一,直接影响光谱的分辨能力和探测灵敏度.利用调制荧光光谱技术获得了超冷长程铯分子超精细振转光谱.通过研究解调参数,即积分时间和灵敏度,发现解调参数对光谱信号的信噪比有重要影响,且依赖关系呈非线性.结合相关实验系统,实现了对光谱信噪比的最优化控制,为进一步研究超冷铯分子长程态振转能级结构奠定了重要的实验基础.     

超冷铯分子0u+(6P3/2)长程态的高灵敏光缔合光谱研究

利用发展的调制俘获损耗荧光光谱技术实验测量了超冷铯分子0_u⁺(6P_3/2)长程态的高灵敏光缔合光谱. 光谱探测范围较国际已有报道扩大了60 cm^-1, 观察到25个长程区域新的振动能级. 通过LeRoy-Bernstein公式对振动束缚能数据进行拟合, 获得了超冷铯分子0_u⁺(6P_3/2)态的长程系数C₃ 为16.103±0.010. 构建了超冷铯分子0_u⁺(6P_3/2)态长程区域的势能曲线.     

超冷铯分子纯长程态转动常数的精密测量

利用调制的俘获损耗光谱技术实验测量了超冷铯分子纯长程0_g^-态的高分辨光谱. 采用双光缔合光谱技术构建了精确的频率差参考信号, 对转动能级的共振频率间隔进行了精确的标定, 获得了转动能级频率间隔与转动量子数的关系. 通过将实验数据拟合到非刚性转动模型, 获得了超冷铯分子纯长程0_g^-态不同振动态的转动常数. 实验结果表明转动常数随振动量子数的增加而线性减小, 线性递减率为-0.41 MHz±0.01 MHz. 关键词： 双光缔合光谱技术 超冷铯分子 转动常数 纯长程态     

超冷铯(60D5/2)2 Rydberg分子的双色光缔合光谱

本文主要从理论和实验上研究超冷铯（60D_5/2）₂ Rydberg分子的双色光缔合光谱.数值计算了铯60D_5/2 Rydberg原子对态的长程电多极相互作用和（60D_5/2）₂ Rydberg分子的绝热势能曲线,获得了（60D_5/2）₂ Rydberg分子的势阱深度和平衡间距.实验上利用双色光缔合超冷铯原子的方法制备了（60D_5/2）₂ Rydberg分子.其中,第一色激光（pulse-A）双光子共振激发种子Rydberg原子A;第二色激光（pulse-B,失谐于分子的束缚能）共振激发第二个Rydberg原子B,原子A与B由分子势阱束缚形成超冷（60D_5/2）₂ Rydberg分子.由脉冲场电离探测技术获得Rydberg分子的光缔合光谱,测量的Rydberg分子的势阱深度与理论计算结果相一致.     

利用双光缔合光谱技术直接测量超冷铯分子0u+(6S1/2+6P1/2)长程态的转动常数的实验研究

实验获得了超冷铯分子6S_1/2+6P_1/2离解限下0_u⁺长程态振动能级v=187的转动常数. 首先利用调制的荧光光谱技术获得了高分辨的转动量子数J=0–6的超冷铯分子纯转动光谱. 利用双光缔合光谱技术, 构建了高精度的频率参考信号, 进而得到了相邻转动能级间的频率间隔. 最后通过非刚性转子模型拟合得到了转动常数和离心畸变常数.     

超冷铷铯极性分子振转光谱的实验研究

利用激光冷却俘获技术在双暗磁光阱中获得高密度的超冷铷原子和铯原子,通过光缔合方法制备超冷铷铯极性分子.采用共振增强双光子电离技术探测基三重态a³∑⁺的铷铯分子,产率约为10⁴/s.通过改变缔合光频率,获得（2）0⁺,（3）0^-,（2）0^-等分子态的高分辨振转光谱,拟合得到相应的转动常数分别为0.00349 cm^-1,0.00649 cm^-1,0.00372 cm^-1.     

飞行时间质谱探测磁光阱中超冷分子离子的实验研究

利用飞行时间质谱探测了由磁光阱中的俘获光和 再泵浦光光缔合作用形成的超冷基态铯分子, 研究了微通道板工作电压、加速电场强度和加速电场持续时间对铯分子离子信号强度的影响. 实验结果与理论模型的拟合一致; 获得了适合实验条件的最优化实验参数, 为进一步研究超冷分子的光缔合光谱和光电离光谱奠定了实验基础.     

铯原子调制转移光谱在激光稳频中的应用

利用铯原子D₂线的调制转移光谱的鉴频特性,实现了光栅外腔式主振荡器-功率放大型(MOPA)半导体激光器相对于铯原子6²S_1/2F=4→6²P_3/2 F’=5超精细跃迁的偏频锁定,在100 ms内激光频率的相对起伏小于±280 kHz.相对于一般的饱和吸收锁频方法而言,调制转移光谱在锁频中的应用不仅彻底消除了Doppler背景对锁频的影响,而且还避免了对激光器直接进行频率扰动而带来的附加频率噪音.     

Research on ultracold cesium molecule long-range states by high-resolution photoassociative spectroscopy

In this paper, an ultra-high resolution photoassociation spectroscopy study on photoassociation of cesium atoms is reported. The cold cesium gas in the magneto-optical trap is illuminated by a photoassociation laser with red-tuning as large as 40 cm⁻¹ below the 6S _1/2 + 6P _3/2 dissociation limit, and the photoassociation to the excited state ultracold molecule is detected. High signal-to-noise ratio is obtained by using the lock-in detection of the fluorescence from the modulated cold Cs atoms. The 0 _g ⁻ , 1_g and 0 _u ⁺ long-range states which correspond to 6S _1/2 + 6P _3/2 dissociation limit are present in the photoassociation spectrum. The effective coefficients of leading long-range interactions and the corresponding vibrational quantum number are obtained using LeRoy-Bernstein Law. It is found that photoassociation process creates rotating molecules and the high J value is a hint that higher partial waves participate in the PA process in the presence of trapping laser. Supported by 973 Program of China (Grant. No. 2006CB921603), the National Natural Science Foundation of China (Grant Nos. 10574084, 60678003, and 60778008), the Special Foundation for State Major Basic Research Program of China (Grant No. 2005CCA06300), and the Youth Science Foundation of Shanxi Province of China (Grant No. 20041013)     

Ultra-high resolution trap-loss spectroscopy of ultracold <Superscript>133</Superscript>Cs atom long-range states in a magnetooptical trap

We present an ultra-high resolution spectroscopic study of the photoassociation of cesium atoms inside a magnetooptical trap using trap-loss detection with photoassociation laser slow scanning. The photoassociation spectra show vibrational levels of three molecular symmetries below the 6S _1/2 + 6P _3/2 dissociation limit. A dynamic model is derived to extract the photoassociation rate from the trap-loss spectrum. Many observed rotational levels are well resolved, which indicate d-wave and higher partial wave contributions to the photoassociation cross section.     

Cold cesium molecules produced directly in a magneto-optical trap

We report on the observation of ultracold ground electric-state cesium molecules produced directly in a magneto- optical trap with a good signal-to-noise ratio. These molecules arise from the photoassociation of magneto-optical trap lasers and they are detected by resonantly enhanced multiphoton ionization technology. The production rate of ultracold cesium molecules is up to 4×10⁴ s^-1. We measure the characteristic time of the ground electric-state cesium molecules generated in the experiment and investigate the Cs₂⁺ molecular ion intensity as a function of the trapping laser intensity and the ionization pulse laser energy. We conclude that the production of cold cesium molecules may be enhanced by using appropriate experimental parameters, which is useful for future experiments involving the production and trapping of ultracold ground electric-state molecules.     

Photoionization and detection of ultracold Cs<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript> molecules through diffuse bands

We present the results of absorption measurements in a cesium vapor around 630 K, together with photoionization spectra through a resonance-enhanced two-photon absorption of ultracold cesium dimers created after photoassociation of ultracold cesium atoms. The maximum efficiency of the ultracold molecule ionization is found for wavelengths where absorption at thermal energies is the strongest, in agreement with our theoretical simulations of both processes, involving the so-called Cs₂ diffuse bands. This result will be helpful for further optimization of such a direct way of detection of ultracold molecules. Received 13 September 2001     

High sensitive photoassociation spectroscopy based on modulated ultra-cold Cs atoms

In this paper, a high sensitive photoassociation spectroscopy based on modulated ultra-cold cesium atoms is reported. The cold cesium gas in the magneto-optical trap is illuminated by a photoassociation laser with red detuning 40 cm^-1 below the 6S _1/2+6P _3/2 dissociation limit and photoassociation to the excited state ultra-cold molecules is observed. The rotationally bound levels of 0_g ^- state are well resolved using the lock-in detection. The 0_g ^-, 1_g and 0_u ⁺ long range states which connect to this dissociation limit are measured. The long-range dipole–dipole interaction constants are determined through a fit of the experimental energy levels. PACS 33.15.Mt; 33.20.Vq; 32.80.Pj     

The laser-intensity dependence of the photoassociation spectrum of the ultracold Cs_2(6S_(1/2) + 6P_(1/2))0_u~+ long-range molecular state

The high-resolution photoassociation spectrum of the ultracold cesium molecular 0_u~+ state below the 6S 1/2 + 6P 1/2 limit is presented in this paper. The saturation of the photoassociation scattering probability is observed from the dependence of the trap-loss probability on the photoassociation laser intensity. The corresponding resonant line width is also demonstrated to increase linearly with increasing photoassociation laser intensity. Our experimental data have good consistency with the theoretical saturation model of Bohn and Julienne Bohn J L and Julienne P S 1999 Phys. Rev. A 60 1].     

Cesium satellite band at 875.2 nm stemming from the Cs 2 0 g + (6 p 2 P 1/2 +6 s 2 S 1/2 ) state

We measured a very distinct satellite band at 875.2 nm between two resonance lines of cesium. Spectral simulation using Spies and Meyer [#!ref1!#] ab initio potential curves and an appropriate transition dipole moment function was compared with experimental profile. Implications of the investigated satellite band at 875.2 nm in the field of ultracold cesium atom collisions are discussed with a special emphasize to new possibilities of the photoassociation of two ground state atoms leading to the formation of ultracold intermediate long-range molecules. Received 07 March 2001 and Received in final form 14 May 2001     

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