Deeply bound cold caesium molecules formed after 0(-)(g) resonant coupling

Translationally cold caesium molecules are created by photoassociation below the 6s + 6p(1/2) excited state and selectively detected by resonance enhanced two photon ionization (RE2PI). A series of excited vibrational levels belonging to the 0(-)(g) symmetry is identified. The regular progression of the vibrational spacings and of the rotational constants of the 0(-)(g) (6s + 6p(1/2)) levels is strongly altered in two energy domains. These deviations are interpreted in terms of resonant coupling with deeply bound energy levels of two upper 0(-)(g) states dissociating into the 6s + 6p(3/2) and 6s + 5d(3/2) asymptotes. A theoretical model is proposed to explain the coupling and a quantum defect analysis of the perturbed level position is performed. Moreover, the resonant coupling changes dramatically the spontaneous decay products of the photoexcited molecules, strongly enhancing the decay into deeply bound levels of the a(3)Σ(+)(u) triplet state and of the X(1)Σ(+)(g) ground state. These results may be relevant when conceiving population transferring schemes in cold molecule systems.     

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     

Formation of cold Cs ground state molecules through photoassociation in the pure long-range state

We report on the formation of translationally cold Cs₂ ground state molecules through photoassociation in the 1_u attractive molecular state below the 6 s _1/2 +6 p _3/2 dissociation limit. The cold molecules are obtained after spontaneous decay of photoassociated molecules in a MOT and in a dark SPOT. We also used polarized atoms, in the f =3, m f =+3Zeeman ground state. Purely asymptotic and adiabatic calculations including hyperfine interaction and rotation are in excellent agreement with observed structures. As expected, the 1_u state is actually a pure long-range state, consisting of paired atoms, uniquely linked by the first terms of the multipole expansion of the electrostatic interaction. A temperature of 20 K has been measured for the molecular cloud. Received 19 July 1999     

Broadband Vibrational Cooling of Cold Cesium Molecules: Theory and Experiments

通过调制的宽带激光脉冲冷却冷的铯分子平动近来被证明同时也是冷却其振动自由度的有效方法. 这样,最初分布在几个振动能级上的冷分子样品的布居可以被转移到被唯一选定的单电子基态X1∑g的振动能级上. 基于使用具有足够宽谱带的激光脉冲对所有已布居的振动态进行重复泵浦,并且使用空间光调制器来限制其频率带宽,这样就可以消除从所选定的能级上产生的激发,从而使分子布居在这个能级上. 本文报道了实验的主要结果,并且通过仔细的计算模拟来讨论包括转动自由度在内的对分子进行“完全”冷却的前景. 由于泵浦过程强烈地依赖于基态和激发     

Accurate asymptotic ground state potential curves of Cs$\mathsf{_2}$ from two-colour photoassociation

Over 100 high lying level energies of the lowest electronic states and in Cs₂ are determined in a -like scheme two-colour photoassociation spectroscopy. The results are analyzed with a coupled channel model using an asymptotic approach, based on nodal lines. From this analysis we determine the long range dispersion coefficient C₆ to 6846.2 15.6 a.u. We also obtain the first experimental determination of the amplitude of the asymptotic exchange term.Received: 4 November 2003, Published online: 20 January 2004PACS: 34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions - 32.80.Pj Optical cooling of atoms; trapping - 03.65.Ge Solutions of wave equations: bound states     

Continuous transfer and laser guiding between two cold atom traps

We have demonstrated and modeled a simple and efficient method to transfer atoms from a first Magneto-Optical Trap (MOT) to a second one. Two independent setups, with cesium and rubidium atoms respectively, have shown that a high power and slightly diverging laser beam optimizes the transfer between the two traps when its frequency is red-detuned from the atomic transition. This pushing laser extracts a continuous beam of slow and cold atoms out of the first MOT and also provides a guiding to the second one through the dipolar force. In order to optimize the transfer efficiency, the dependence of the atomic flux on the pushing laser parameters (power, detuning, divergence and waist) is investigated. The atomic flux is found to be proportional to the first MOT loading rate. Experimentally, the transfer efficiency reaches 70%, corresponding to a transfer rate up to 2.7×10⁸ atoms/s with a final velocity of 5.5 m/s. We present a simple analysis of the atomic motion inside the pushing–guiding laser, in good agreement with the experimental data.     

Analyzing powers of valence and inner neutron-hole states in 115Sn via the 116Sn(d, t) reaction

The reaction ¹¹⁶Sn($\text{d}$, t)¹¹⁵Sn up to 7.5 MeV excitation energy has been studied at 40 MeV incident energy using a vector polarized deuteron beam. The measured analyzing power reveals strong J-dependence effects and has been used to clearly assign the spin of a number of low-lying states in the ¹¹⁵Sn nucleus. At higher excitation energy, a broad and fragmented bump is observed between 3.7 and 6.0 MeV in ¹¹⁵Sn. This work reports on one of the first attempts to determine the spin of such structure through polarization measurements. The analyzing power data indicates a mixing of spins $\text{J =}\text{9}\text{2}\text{,}\text{1}\text{2}$, in agreement with the excitation of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{and}\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ inner neutron-hole strengths in the ¹¹⁵Sn nucleus. In addition, some $\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ components are observed around ~ 4.6 MeV excitation energy.     

Entanglement of two ground state neutral atoms using Rydberg blockade

We report on our recent progress in trapping and manipulation of internal states of single neutral rubidium atoms in optical tweezers. We demonstrate the creation of an entangled state between two ground state atoms trapped in separate tweezers using the effect of Rydberg blockade. The quality of the entanglement is measured using global rotations of the internal states of both atoms.     

Loading a dipole trap from an atomic reservoir

Loading a dipole trap from an atomic reservoir is considered to be an efficient method for the preparation of trapped atoms at high density, which has led to notable results for the case of Rb and Cr atoms. It was also theoretically predicted to provide efficient loading also in the cesium case. In this article, we report on the experimental study of the loading of a single-arm and of a crossed dipole trap for cesium atoms. This study is performed by comparing several types of reservoirs from which the atoms are loaded: a magnetic trap, a Dark-SPOT and a compressed MOT. In all cases the number of atoms is found to decrease shortly after the beginning of the loading process. A few possible phenomena leading to such a behavior, namely the limited reservoir lifetime and/or a possible heating in the reservoir, are discussed. The loading dynamics is fitted by a phenomenological rate equation. From an experimental point of view, the reservoir loading method can be considered efficient in terms of number of transferred atoms for the single arm dipole trap. On the contrary, it does not seem to provide, for the case of cesium atoms in a crossed dipole trap, an attractive alternative in comparison with existing loading methods such as Raman sideband cooling.     

Use of Rydberg atoms to control electron temperatures in ultracold plasmas

We investigate the idea of adding Rydberg atoms to an ultracold plasma to control the electronic temperature of the plasma. We show that a certain amount of control is indeed possible, and discuss limitations for the extent of electron cooling. Experimental data are found to be in good agreement with numerical simulations.