共查询到20条相似文献,搜索用时 15 毫秒
1.
L. G. Marcassa V. A. Nascimento L. L. Caliri A. Caires D. V. Magalhães V. S. Bagnato 《Laser Physics》2006,16(12):1722-1725
In this paper, we report observation of an enhancement of the ground state molecule Rb2 formation in a Rb magneto-optical trap due to a photoassociation laser. Such an enhancement effect is due to flux enhancement of atomic pairs at short internuclear distances. Our experimental observations consist in the measurement of the molecular formation rate constant due to a probe laser as a function of the trap laser intensity. The results are compared with a simple semi-classical model, showing good agreement. We conclude that the production of cold Rb2 may be enhanced using appropriate laser parameters; this may be useful for future experiments involving production and trapping of ultracold ground state molecules. 相似文献
2.
3.
4.
5.
A. Mosk S. Kraft M. Mudrich K. Singer W. Wohlleben R. Grimm M. Weidemüller 《Applied physics. B, Lasers and optics》2001,73(8):791-799
We present the first simultaneous trapping of two different ultracold atomic species in a conservative trap. Lithium and cesium
atoms are stored in an optical dipole trap formed by the focus of a CO2 laser. Techniques for loading both species of atoms are discussed and observations of elastic and inelastic collisions between
the two species are presented. A model for sympathetic cooling of two species with strongly different mass in the presence
of slow evaporation is developed. From the observed Cs-induced evaporation of Li atoms we estimate a cross-section for cold
elastic Li-Cs collisions.
Received: 1 August 2001 / Published online: 23 November 2001 相似文献
6.
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6S1/2+6P3/2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。 相似文献
7.
The formation of ultracold metastable RbCs molecules is observed in a double species magneto-optical trap through photoassociation below the 85Rb(5S1/2) + 133Cs(6P3/2) dissociation limit followed by spontaneous emission. The molecules are detected by resonance enhanced two-photon ionization. Using accurate quantum chemistry calculations of the potential energy curves and transition dipole moment, we interpret the observed photoassociation process as occurring at short internuclear distance, in contrast with most previous cold atom photoassociation studies. The vibrational levels excited by photoassociation belong to the 5th 0+ or the 4th 0? electronic states correlated to the Rb(5P1/2, 3/2) + Cs(6S1/2) dissociation limit. The computed vibrational distribution of the produced molecules shows that they are stabilized in deeply bound vibrational states of the lowest triplet state. We also predict that a noticeable fraction of molecules is produced in the lowest level of the electronic ground state. 相似文献
8.
S.D. Kraft J. Mikosch P. Staanum J. Deiglmayr J. Lange A. Fioretti R. Wester M. Weidemüller 《Applied physics. B, Lasers and optics》2007,89(4):453-457
We have realized a high-resolution time-of-flight mass spectrometer combined with a magneto-optical trap. The spectrometer
enables excellent optical access to the trapped atomic cloud using specifically devised acceleration and deflection electrodes.
The ions are extracted along a laser beam axis and deflected onto an off-axis detector. The setup is applied to detect atoms
and molecules photoassociated from ultracold atoms. The detection is based on resonance-enhanced multi-photon ionization.
Mass resolution up to m/Δmrms=1000 at the mass of 133Cs is achieved. The performance of this spectrometer is demonstrated in the detection of photoassociated ultracold 7Li133Cs molecules near a large signal of 133Cs ions.
PACS 07.75.+h; 32.80.Rm; 37.10.Gh 相似文献
9.
C.M. Dion O. Dulieu D. Comparat W. de Souza Melo N. Vanhaecke P. Pillet R. Beuc S. Milošević G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):365-370
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 相似文献
10.
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
11.
Photoassociation of ultracold atoms induced by chirped picosecond pulses is analyzed in a non-perturbative treatment by following the wavepacket dynamics on the ground and excited surfaces. The initial state is described by a Boltzmann distribution of stationary continuum states. The chosen example is photoassociation of cesium atoms at temperature
K from the
continuum to bound levels in the external well of the 0
g
-(6s + 6p
3/2) potential. We study how the modification of the pulse characteristics (carrier frequency, duration, linear chirp rate and intensity) can enhance the number of photoassociated molecules and suggest ways of optimizing the production of stable molecules.Received: 30 June 2004, Published online: 23 November 2004PACS:
33.80.Ps Optical cooling of molecules; trapping - 33.80.-b Photon interactions with molecules - 33.90. + h Other topics in molecular properties and interactions with photons - 33.80.Gj Diffuse spectra; predissociation, photodissociation 相似文献
12.
In this paper, we report the measurement of Rb2 molecule formation rate constant due to a two body process in a magneto-optical trap as a function of the sample temperature.
The ground state molecules are detected by two-photon ionization, through the intermediate a
3Σ
u
+ → 23Π
g
molecular band. Our results show that the Rb2 molecules formed in the MOT could be due to a wave shape resonance, which enhances the molecule formation rate. This effect
may be used to enhance the molecule production; and therefore it maybe important to future experiments involving production
and trapping of cold ground state molecules. 相似文献
13.
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
14.
J.P. Shaffer W. Chalupczak N.P. Bigelow 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):323-330
We present direct measurements of the overall trap loss rate and the fine structure changing collision rate for ultracold
cesium atom confined in a magneto-optical trap over an intensity range of 5 mW/cm2 to 200 mW/cm2. This set of simultaneous measurements allows the accurate extraction and separation of the fine structure changing rate
and the radiative escape rate as these two processes compete with one another to determine the overall trap loss rate.
Received 4 December 1998 and Received in final form 18 March 1999 相似文献
15.
S. K. Tokunaga W. Skomorowski P. S. Żuchowski R. Moszynski J. M. Hutson E. A. Hinds M. R. Tarbutt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(1-2):141-149
We consider how trapped molecules can be sympathetically cooled by ultracold atoms. As a prototypical system, we study LiH molecules co-trapped with ultracold Li atoms. We calculate the elastic and inelastic collision cross sections of 7LiH + 7Li with the molecules initially in the ground state and in the first rotationally excited state. We then use these cross sections to simulate sympathetic cooling in a static electric trap, an ac electric trap, and a microwave trap. In the static trap we find that inelastic losses are too great for cooling to be feasible for this system. The ac and microwave traps confine ground-state molecules, and so inelastic losses are suppressed. However, collisions in the ac trap can take molecules from stable trajectories to unstable ones and so sympathetic cooling is accompanied by trap loss. In the microwave trap there are no such losses and sympathetic cooling should be possible. 相似文献
16.
V. N. Lokhman D. D. Ogurok E. A. Ryabov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):59-67
We report about effective ionization of iodine atoms and CF3I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation
of the CF3I molecules is the I+ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on
the intensity
of the ion signal and the shape of its time-of-flight peak. Based on the
analysis of the results obtained, we have suggested the mechanism of this
effect. The conclusion drawn is that the ionization of the iodine atoms by
the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in
turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and
the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground
state I(2P3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization
from the metastable state I*(2P1/2). The ionization of the CF3I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation
of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms. 相似文献
17.
We have investigated how the formation of ultracold molecules in a rubidium magneto-optical trap is affected by the application of positively-chirped femtosecond laser pulses. The application of femtosecond pulses resulted in a reduction, rather than an increase, in the rate of detection of 85Rb2 and 87Rb2 triplet ground-state molecules, and compared this to the effects of non-chirped pulses, continuous-wave light, and the formation rate when no additional light was applied. A dependence on the amount of chirp of the femtosecond laser pulses suggests that the reduction in the molecular signal is the result of a coherent effect, and provides a promising indication that coherent control could be used to engineer the production of ultracold molecules. 相似文献
18.
J. Lozeille A. Fioretti C. Gabbanini Y. Huang H. K. Pechkis D. Wang P. L. Gould E. E. Eyler W. C. Stwalley M. Aymar O. Dulieu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):261-269
We present detailed experimental spectra and accurate theoretical interpretation of resonance-enhanced
two-photon ionization of ultracold rubidium molecules in the
14000–17000 cm-1 transition energy range. The dimers are formed in a
magneto-optical trap by photoassociation followed by radiative decay into the a 3Σu+
lowest triplet state. The theoretical treatment of the process, which reproduces the main features
of the spectra, takes into account the photoassociation and decay steps as well as the resonant ionization through the manifold
of intermediate gerade states correlated to the 5S + 4D limit. In particular, the energy of the v=1 level of the
potential well has been determined for the first time. In addition, a tight constraint has been put on the position of the
a 3Σu+
repulsive wall. Finally, magnetic trapping of
rubidium molecules in the a 3Σu+ state is demonstrated.
Electronic supplementary material Online Material 相似文献
19.
We report on the trapping of radioactive atoms for a variety of nuclear, atomic, and applied physics investigations. To date
we have trapped 5 different radioisotopes of rubidium and cesium (82–84Rb+135,137Cs) using a magneto-optical trap (MOT) coupled to a mass separator. By optimizing the efficiency of this system, we have been
able to trap as many as 6 million radioactive atoms and detect as few as 100. This technology is being applied in three different
areas: (1) the parity-violating, β-decay asymmetry measurement of polarized 82Rb; (2) the study of ultracold fermionic 84Rb atoms; and (3) the use of MOTs for the ultrasensitive detection of selected radioactive species. Although all of these
projects are in a formative stage of development, we highlight the progress that we have made in: (1) the trapping of 82Rb atoms in double MOT system; (2) the hyperfine structure measurement of the 5P1/2 and 5P3/2 levels in 82Rb; (3) the simultaneous trapping of 84Rb and 87Rb in overlapping MOTs; and (4) the first trapping and isotopic ratio measurement of 135Cs and 137Cs in a MOT.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
In this paper,ultracold atoms and molecules in a dark magneto-optical trap(MOT) are studied via depumping the cesium cold atoms into the dark hyperfine ground state.The collision rate is reduced to 0.45s-1 and the density of the atoms is increased to 5.6×1011cm-3 when the fractional population of the atoms in the bright hyperfine ground state is as low as 0.15.The vibrational spectra of the ultracold cesium molecules are also studied in a standard MOT and in a dark MOT separately.The experimental results are analyzed by using the perturbative quantum approach. 相似文献