共查询到20条相似文献,搜索用时 15 毫秒
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<正>We report the experimental achievement of ~(87)Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency(RF) induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave radiation driving the ~(87)Rb atoms to transit from the ground-state hyperfine state |F=2,m_F= 2〉to |F=l,m_F=1〉.Compared with RF-induced evaporation,~(87)Rb atoms are hardly to achieve pure condensate by microwave evaporation cooling due to the effect of atoms in the |F=1,m_F=1〉state being pumped back into the trapping |F=2,m_F=1〉state. 相似文献
3.
We develop a simple and practical scheme to apply sideband cooling to a cloud of rubidium atoms. A sample containing 4 × 10~(70) ~(87)Rb is trapped in a far red detuned optical lattice. Through optimizing the relevant parameters, i.e., laser detuning, magnetic field, polarization, and duration time, a temperature around 1.5 μK and phase space density close to 1/500 are achieved. Compared with polarization gradient cooling, the temperature decreases by around one order of magnitude. This technique could be used in high precision measurement such as atomic clocks and atom interferometer. It could also serve as a precooling means before evaporation cooling in a dipole trap, and may be a promising method of achieving quantum degeneracy with purely optical means. 相似文献
4.
D. Sukachev K. Chebakov A. Sokolov A. Akimov N. Kolachevsky V. Sorokin 《Optics and Spectroscopy》2011,111(4):633-638
We demonstrated laser cooling and trapping of thulium atoms at sub-Doppler temperatures in a magneto-optical trap (MOT). Up
to 3 × 106 thulium atoms were trapped in the MOT at temperatures down to 25(5) μK which is approximately 10 times lower than the Doppler
limit. The lifetime of atoms in the MOT varied between 0.3–1.5 s and was restricted mostly by optical leaks from the upper
cooling level. The lower limit for the leaking rate was estimated to be 22(6) s−1. Due to a big magnetic moment of Tm atoms, a part of them were trapped in a magnetic trap from the quadrupole field of the
MOT. We observed about 3 × 104 purely magnetically trapped atoms at temperature of 25 μK with a lifetime in the trap of 0.5 s. Also we set up a “dark” MOT
consisting of six crossed hollow beams which increased the number of trapped atoms by a factor of 5 leading to 1.5 × 107 atoms at the expense of higher temperature. 相似文献
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Ling Xiao Xu-cheng Wang Ben-chang Zheng Yan-ling Meng Hua-dong Cheng Liang Liu Yu-zhu Wang 《Optik》2012,123(5):442-446
Kinetic behavior of cold 87Rb atoms in integrating sphere is presented under adiabatic release. Decay time of cold atom cloud is deduced by calculation of residual cold atom number evolution under adiabatic release and agrees well with our experimental observation. Number evolutions of residual cold atoms under different kinds of acceleration have been studied in detail. Sequence laser pulse cooling is key technique for the successive operation of cold atom clock. The process of laser pulse cooling is numerically simulated and fitted with experiments, optimized distribution of cooling and dead time to get enough cold atoms is put forward to satisfy the demand of cold atom clock. 相似文献
6.
Shevy Y 《Physical review letters》1990,64(24):2905-2908
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Xin-ye XU Wen-li WANG Qing-hong ZHOU Guo-hui LI Hai-ling JIANG Lin-fang CHEN Jie YE Zhi-hong ZHOU Yin CAI Hai-yao TANG Min ZHOU 《Frontiers of Physics in China》2009,4(2):160-164
The experiments on the laser cooling and trapping of ytterbium atoms are reported, including the two-dimensional transversal
cooling, longitudinal velocity Zeeman deceleration, and a magneto-optical trap with a broadband transition at a wavelength
of 399 nm. The magnetic field distributions along the axis of a Zeeman slower were measured and in a good agreement with the
calculated results. Cold ytterbium atoms were produced with a number of about 107 and a temperature of a few milli-Kelvin. In addition, using a 556-nm laser, the excitations of cold ytterbium atoms at 1S0-3P1 transition were observed. The ytterbium atoms will be further cooled in a 556-nm magneto-optical trap and loaded into a three-dimensional
optical lattice to make an ytterbium optical clock.
相似文献
8.
Fujio Shimizu 《Hyperfine Interactions》1992,74(1-4):259-267
The characteristics of laser cooling and trapping of Li, Ne, Ar, Kr, Ca, and Sr are described. The effect of the hyperfine
structure, level multiplicity and population leakage on the trapping efficiency are discussed. 相似文献
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N. A. Matveeva A. V. Taichenachev A. M. Tumaĭkin V. I. Yudin 《Journal of Experimental and Theoretical Physics》2007,105(2):306-313
A quasi-classical theory of laser cooling is applied to the analysis of cooling of unbound atoms with the angular momenta 1/2 in the ground and excited states in a one-dimensional nondissipative optical lattice. In the low-saturation limit with respect to the pumping field, the mechanisms of cooling can be interpreted within the framework of an effective two-level system of ground-state sublevels. In the limit of weak Raman transitions, the mechanism of cooling of unbound atoms is similar to the Doppler mechanism known in the theory of a two-level atom; in the limit of strong transitions, the mechanism of cooling is analogous to the well-known Sisyphys mechanism. In the slow-atom approximation, analytical expressions are obtained for the friction (drag) coefficient and the induced and spontaneous diffusion, and the kinetic temperature is estimated. 相似文献
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B. B. Zelener S. A. Saakyan V. A. Sautenkov A. M. Akulshin E. A. Manykin B. V. Zelener V. E. Fortov 《JETP Letters》2014,98(11):670-674
A setup for laser cooling and confining of 7Li atoms in a magneto-optical trap has been built. The possibility of cooling and trapping of 7Li atoms in a wide range of frequency detuning of the cooling laser has been proved experimentally. Independent information on the density and number of ultracold 7Li atoms on various ground-state sublevels, as well as on the temperature of the atoms, has been obtained with the use of a probing tunable laser. This information is important for preparing an ultracold plasma and Rydberg matter. 相似文献
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P. L. Chapovsky 《JETP Letters》2012,95(3):132-136
A setup for preparing the Bose-Einstein condensate of rubidium atoms has been built. The condensate consists of 105–106
87Rb atoms in the hyperfine state F
g = 2 of the ground electronic state. Three key indications of condensation—a sharp increase in the phase-space density of
atoms, the threshold emergence of two fractions in the cloud, and anisotropic expansion of the condensate—have been observed. 相似文献
12.
Laser cooling below a photon recoil with three-level atoms 总被引:1,自引:0,他引:1
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D. Lucas P. Horak G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):261-267
We study one-dimensional Sisyphus cooling on the transition of
87
Rb atoms in the electric field created by two counter-propagating linearly polarized laser beams with an angle of between the polarization directions. The neighbouring F
'=0 and F
'=2 excited states are found to play an important role in the cooling mechanism, e.g., by inhibiting a significant population of the velocity-selective dark state. Our experimental data, such as temperatures
and probe absorption coefficients, agree well with the results of quantum Monte-Carlo wavefunction simulations.
Received 26 November 1998 and Received in final form 20 April 1999 相似文献
14.
The effect of microwave radiation on the resonance fluorescence of a cloud of cold 85Rb atoms in a magnetooptical trap is studied. The radiation frequency was tuned near the hyperfine splitting frequency of rubidium atoms in the 5S ground state. The microwave field induced magnetic dipole transitions between the magnetic sublevels of the 5S (F=2) and 5S (F=3) states, resulting in a change in the fluorescence signal. The resonance fluorescence spectra were recorded by tuning the microwave radiation frequency. The observed spectra were found to be substantially dependent on the transition under study and the frequency of a repump laser used in the cooling scheme. 相似文献
15.
We have carried out distorted wave calculations for electron impact 5
2P, 6 2S and 4 2D excitations of rubidium atom at incident electron energies in the range of 10-200 eV. Results are presented for differential and total cross-sections of these excitations, Stokes parameters of the excitation of the fine-structure resolved and unresolved 5 2P and 4 2D states, complete experiment parameters for the excitation of 5 2P state and the STU spin parameters of its fine structure states. Good agreement is found on comparison of our results with the available experimental data and the earlier theoretical calculations. Except for the resonance 5
2P transition no earlier calculations were reported for the excitation of the higher 6 2S and 4 2D states.Received: 25 February 2004, Published online: 22 June 2004PACS:
34.80.Dp Atomic excitation and ionization by electron impact - 34.80.Nz Spin dependence of cross-sections; polarized electron beam experiments 相似文献
16.
P. L. Chapovsky 《Journal of Experimental and Theoretical Physics》2005,100(5):911-919
The characteristics of a magneto-optical trap (MOT) using small-diameter cooling laser beams are considered. Trapping and cooling of Rb atoms from the surrounding gas of warm atoms takes place in the trap. A compact (140 μm) and stable atomic cloud is obtained with a density of 7 × 1010 cm?3, which is three orders of magnitude higher than the density of the surrounding gas. 相似文献
17.
We report on a novel mechanism that allows for strong laser cooling of atoms that do not have a closed cycling transition. This mechanism is observed in a magneto-optical trap (MOT) for erbium, an atom with a very complex energy level structure with multiple pathways for optical-pumping losses. We observe surprisingly high trap populations of over 10(6) atoms and densities of over 10(11) atoms cm(-3), despite the many potential loss channels. A model based on recycling of metastable and ground state atoms held in the quadrupole magnetic field of the trap explains the high trap population, and agrees well with time-dependent measurements of MOT fluorescence. The demonstration of trapping of a rare-earth atom such as erbium opens a wide range of new possibilities for practical applications and fundamental studies with cold atoms. 相似文献
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P. S. Ganas 《Zeitschrift für Physik A Hadrons and Nuclei》1982,305(1):21-24
An analytic central potential containing two adjustable parameters is used to generate wave functions for the ground and excited states of the rubidium atom. The two parameters are chosen so that the potential reproduces accurately known values of optical oscillator strengths for the 5s?np (n≧5) transitions. Using the Born approximation, we calculate generalized oscillator strengths and integrated cross sections up to 5 keV for the 5s?np excitations. Reasonable agreement with experimental data is obtained. 相似文献