共查询到20条相似文献,搜索用时 453 毫秒
1.
2.
Boussen S. Hoang N. Guibal S. Zahzam N. Pruvost L. Marescaux D. Pinard J. Pillet P. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,28(2):259-266
Bose-Einstein condensation (BEC) in a atomic cesium gas prepared in a low field seeker Zeeman sublevel and confined in a magnetic trap has been thwarted by a high cross-section of inelastic spin-flip collisions. A recent experiment [1] succeeded in reaching BEC for cesium atoms using all optical methods and tuning the scattering length. We will discuss a hybrid magnetic and optical trap for cesium atoms in the true hyperfine ground state, the high field seeker Zeeman sublevel, F = m
F
= 3. Although this trap allows only one-dimensional (1D) evaporative cooling, we show that a route towards BEC with such a trap should be possible. We present simulations of 1D evaporative cooling, which shows that a high phase space density (PSD) of 0.1 could be reached in less than 10 seconds.Received: 25 July 2003PACS:
03.75.Hh Static properties of condensates; thermodynamical, statistical and structural properties - 05.30.Jp Boson systems - 32.80.Pj Optical cooling of atoms; trappingLaboratoire Aimé Cotton is associated with University of Paris-Sud. 相似文献
3.
为了制备适于原子干涉仪实验的低温锂原子样品,开展了锂原子的塞曼减速及与磁光阱囚禁相关的实验研究.设计并实现了一种结构紧凑的腔体内冷式多级线圈叠加的塞曼减速器,将速度小于600 m/s的7Li原子减速到60 m/s,磁光阱装载速率为5×108/s,囚禁原子数目1×109个,原子团的最低温度约为220±30μK.研究了光学黏胶中7Li原子的寿命与囚禁光频率失谐量的关系.这些结果为进一步开展7Li原子亚多普勒冷却、光势阱蒸发冷却以及原子干涉仪实验奠定了基础. 相似文献
4.
D. Sukachev A. Sokolov K. Chebakov A. Akimov N. Kolachevsky V. Sorokin 《JETP Letters》2010,92(10):703-706
Sub-Doppler laser cooling in a magneto-optical trap for thulium atoms at a wavelength of 410.6 nm has been experimentally
studied. Without any dedicated molasses period of sub-Doppler cooling, the cloud of 3 × 106 atoms at a temperature of 25(5) μK was observed. The measured temperature is significantly lower than the Doppler limit of
240 μK for the cooling transition at 410.6 nm. The high efficiency of the sub-Doppler cooling process is due to a near-degeneracy
of the Landé g-factors of the lower 4f
136s
2 (J = 7/2) and the upper 4f
125d
3/26s
2 (J = 9/2) cooling levels. 相似文献
5.
Single atoms transferring between a magneto-optical trap and a far-off-resonance optical dipole trap 下载免费PDF全文
Based on our work on single cesium atoms trapped in a
large-magnetic-gradient vapour-cell magneto-optical trap (MOT), the
signal-to-noise ratio (SNR) is remarkably improved. Also a
far-off-resonance optical dipole trap (FORT) formed by a
strongly-focused 1064~nm single frequency Nd:YVO4 laser beam is
introduced. One cesium atom is prepared in the MOT, and then it can
transfer successfully between the MOT and the FORT which is
overlapped with the MOT. Utilizing the effective transfer, the
lifetime of single atoms trapped in the FORT is measured to be
6.9± 0.3~s. Thus we provide a system where the atomic qubit can
be coherently manipulated. 相似文献
6.
7.
O. N. Prudnikov A. V. Taichenachev V. I. Yudin E. M. Rasel 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(12):1420-1428
The possible deep laser cooling of 24Mg atoms in a deep optical lattice in the presence of an additional pumping field resonant to the narrow 3s3s1S0 → 3s3p3P1 (λ = 457 nm) optical transition is studied. Two quantum models of the laser cooling of atoms in the optical trap are compared. One is based on the direct numerical solution to the kinetic quantum equation for an atomic density matrix; it considers both optical pumping and quantum recoil effects during interaction between the atoms and field photons. The second, simplified model is based on decomposing the states of the atoms over the levels of vibration in the optical trap and analyzing the evolution of these states. The comparison allows derivation of optical field parameters (pumping field intensity and detuning) that ensure cooling of the atoms to minimal energies. The conditions for fast laser cooling in an optical trap are found. 相似文献
8.
L.R. Wang J. Ma C.Y. Li J.M. Zhao L.T. Xiao S.T. Jia 《Applied physics. B, Lasers and optics》2007,89(1):53-57
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 0g
- state are well resolved using the lock-in detection. The 0g
-, 1g and 0u
+ 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 相似文献
9.
T. W. Hodapp C. Gerz C. Furtlehner C. I. Westbrook W. D. Phillips J. Dalibard 《Applied physics. B, Lasers and optics》1995,60(2-3):135-143
We have studied the expansion of a small cloud of85Rb atoms in three-dimensional optical molasses (lin lin and + – – configurations) and observed diffusive motion. We determined the spatial-diffusion coefficients for various laser intensities and detunings, and compared them (in the case of lin lin molasses) to values calculated from friction and momentum-diffusion coefficients of a one-dimensional (1D) theory of laser cooling. The predicted variations of the spatial-diffusion coefficient with laser intensity and detuning are in good qualitative agreement with the experimental data. We found that the minimal value observed experimentally, 6 × 10–4 cm2/s, lies within a factor of 3 of the 1D theoretical minimum, , 26/M, whereM is the atomic mass.Dedicated to H. Walther on the occassion of his 60th birthday 相似文献
10.
M. D. Plimmer N. Castagna G. Di Domenico P. Thomann A. V. Taichenachev V. I. Yudin 《JETP Letters》2005,82(1):17-21
We describe transverse collimation of a continuous cold cesium beam (longitudinal temperature 75 μK) induced by a two-dimensional, blue-detuned near-resonant optical lattice. The mechanism described for a lin-‖-lin configuration is made possible by the application of a transverse magnetic field B⊥. The phenomenon described differs from gray molasses, for which any small magnetic field degrades cooling, as well as from magnetically induced laser cooling in red-detuned optical molasses, where there are no dark states. The lowest transverse temperature is experimentally found to vary as B ⊥ 2 . The collimated flux density shows a dip as a function of B⊥, the width of which is proportional to the cube root of the laser intensity, general features predicted by our semiclassical model. This technique provides a sensitive tool for canceling transverse magnetic fields in situ at the milligauss level. 相似文献
11.
The investigation of spin-exchange collisions between optically oriented cesium atoms in the ground 2 S 1/2 state and nitrogen atoms in the ground 4 S 3/2 state reveals an anomalous behavior of the magnetic resonance signal of cesium atoms in the afterglow in an N2-Ar mixture, namely, the magnetic resonance signal is slowly enhanced during the time interval between the high-frequency pulses exciting a discharge in the absorption cell. It is found that such a behavior of the magnetic resonance signal is explained by a slow change in the concentration of nitrogen atoms in the absorption cell, which affects the magnetic resonance of cesium atoms via efficient spin exchange. 相似文献
12.
Coherent propagation of atomic-matter waves in a one-dimensional optical lattice is studied. Wave packets of cold two-level
atoms propagate simultaneously in two optical potentials in a dressed-state basis. Three regimes of the wave-packet propagation
are specified by the quantity Δ2
/ω
D
, where Δ and ω
D
are the dimensionless atom–laser detuning and the Doppler shift, respectively. At Δ2
/ω
D
≫ 1, the propagation is essentially adiabatic, at Δ2
/ω
D
≪ 1, it is (almost) resonant, and at Δ2 ≃ ω
D
, the wave packets propagate nonadiabatically, splitting at each node of the standing wave. The latter means that the atom
makes a transition from one potential to the other one when crossing each node, and the probability of that transition is
given by a Landau–Zener-like formula. All the regimes of propagation are studied with δ-like and Gaussian wave packets in the momentum and position spaces. Varying the control parameters, we can create wave packets
trapped in a well of optical potentials and moving ballistically in a given direction in close analogy with point-like atoms.
Within some range of the parameters, we force the atom to move in a pure quamtum-mechanical manner in such a way that a part
of the packet is trapped in a well, and the other part propagates ballistically. The propagation modes are found to be characterized
by different types of time evolution of the uncertainty product and the Wigner function. 相似文献
13.
We demonstrate an experimental setup for the production of a beam source of cold 87Rb atoms. The atoms are extracted from a trapped cold atomic cloud in an unbalanced three-dimensional magneto-optical trap. Via a radiation pressure difference generated by a specially designed leak tunnel along one trapping laser beam, the atoms are pushed out continuously with low velocities and a high flux. The most-probable velocity in the beam is varied from 9 m/s to 19 m/s by varying the detuning of the trapping laser beams in the magneto-optical trap and the flux can be tuned up to 4×109 s-1 by increasing the intensity of the trapping beams. We also present a simple model for describing the dependence of the beam performance on the magneto-optical trap trapping laser intensity and the detuning. 相似文献
14.
O. N. Prudnikov A. V. Taichenachev A. M. Tumaikin V. I. Yudin 《Journal of Experimental and Theoretical Physics》2004,98(3):438-454
The kinetics of atoms with degenerate energy levels in the field produced by elliptically polarized waves is considered in the semiclassical approximation. Analytic expressions for the force acting on an atom and for the diffusion coefficient in the momentum space are derived for the optical transition J g =1/2→J e = 1/2 in the slow atom approximation. These expressions are valid for an arbitrary one-dimensional configuration of the light field and for an arbitrary intensity. The peculiarities of the atomic kinetics are investigated in detail; these peculiarities are associated with ellipticity of light waves and are absent in particular configurations formed by circularly or linearly polarized waves, which were considered earlier. 相似文献
15.
For the case of cesium atoms optically oriented in a mixture of cesium and rubidium vapors, the temperature dependence of the frequency shift of a magnetic resonance excited in a set of Zeeman sublevels for two hyperfine states of 87Rb 5s 2 S 1/2 atoms. It is shown that, in a weak magnetic field of about 2 × 10?6 T, this shift is determined by the spin-exchange interaction of rubidium atoms with optically oriented 133Cs atoms. 相似文献
16.
A. V. Bezverbnyi O. N. Prudnikov A. V. Taichenachev A. M. Tumaikin V. I. Yudin 《Journal of Experimental and Theoretical Physics》2005,101(4):584-596
An analysis of general characteristics of light-induced forces is presented for arbitrary monochromatic masks in which optical pumping of atoms and spontaneous emission play an important role. Dependence of regions of localization on detuning and ellipticity is determined for cyclic transitions of two types: J å J with half-integer J and J å J + 1 with arbitrary J. Numerical simulations of atomic beam focusing with one-and two-dimensional light masks show that spatial atom distributions with narrow features and high contrast can be formed in dissipative masks. In particular, spherical aberration is substantially reduced when the pumping field is tuned to a J å J + 1 transition with large J in lin ~ lin configuration as compared to nondissipative masks. 相似文献
17.
Jia Su Yonghua Wu M. Patrick McCormick Liqiao Lei Robert B. Lee III 《Applied physics. B, Lasers and optics》2014,115(1):61-67
Two methods to load a microtrap consisting of two concentric microwire loops of radii 300 and 660 μm carrying oppositely oriented currents are demonstrated. Atoms can be directly loaded into the microtrap from a surface magneto-optical trap or alternatively using a far-off resonance optical dipole trap (FORT) as an intermediate step. About 1 × 105 87Rb atoms can be loaded into the microtrap using either technique although the FORT achieves a lower temperature. The FORT is well suited to loading a linear array of 3 microtraps that are aligned with the propagation direction of the infrared laser. Atoms can be trapped in either the $5S_{1/2}\;F=1$ or 2 ground state hyperfine level. The position of the microtrapped atom cloud can be precisely adjusted using a bias magnetic field over a distance of 350 to slightly <50 μm from the atom chip surface. 相似文献
18.
Wang LiRong Ma Jie Ji WeiBang Wang GuiPing Xiao LianTuan Jia SuoTang 《中国科学G辑(英文版)》2008,51(2):147-156
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
−
, 1g 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) 相似文献
19.
The rate constant for spin exchange in a system consisting of a metastable helium atom and an alkali-metal atom is determined.
An experiment on optical orientation of atoms established that the rate constant for spin exchange in a collision of a metastable
23
S
1 helium atom with a cesium atom in the 62
S
1/2 ground state equals (2.8±0.8)×10−9 cm3 s−1. The rate constant for chemoionization of cesium atoms by metastable helium atoms was determined at the same time to be (1.0±0.3)×109 cm3s−1.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 145–148 (10 August 1997) 相似文献
20.
M. Lontano D. Ryutov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):347-351
We demonstrate the in situ detection of cold 87Rb atoms near a dielectric surface using the absorption of a weak, resonant evanescent wave. We have used this technique in
time of flight experiments determining the density of atoms falling on the surface. A quantitative understanding of the measured
curve was obtained using a detailed calculation of the evanescent intensity distribution. We have also used it to detect atoms
trapped near the surface in a standing-wave optical dipole potential. This trap was loaded by inelastic bouncing on a strong,
repulsive evanescent potential. We estimate that we trap 1.5×104 atoms at a density 100 times higher than the falling atoms.
Received 14 May 2002 Published online 8 October 2002
RID="a"
ID="a"e-mail: spreeuw@science.uva.nl 相似文献