共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
A. Fioretti E. Arimondo A. Crubellier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):219-225
The measurements of fine-structure changing collisions in a cesium magneto-optical trap, reported in a previous work [A. Fioretti
et al., Phys. Rev. A 55, R3999 (1997)], are reanalyzed within a model based on the flux enhancement effect, which takes place in cold atomic collisions.
In the present analysis, we consider the cooperative effect of the long-range and the shorter-range excitation by the strong
trap laser. We evidence also the important role of the hyperfine structure of the Cs2 molecular levels asymptotically connected to the ground-state and excited-state dissociation limits.
Received 22 July 1999 and Received in final form 4 May 2000 相似文献
3.
A. Browaeys J. Poupard A. Robert S. Nowak W. Rooijakkers E. Arimondo L. Marcassa D. Boiron C. I. Westbrook A. Aspect 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):199-203
We have measured the two body loss rate in a magneto-optical trap containing triplet metastable He atoms. We find a rate constant
cm3/s at a -8 MHz detuning, with an uncertainty of a factor 2. This measurement is in disagreement with a recent experiment which
measures the absolute, ion-producing collision rate, but agrees with several other published measurements.
Received 20 April 1999 and Received in final form 12 July 1999 相似文献
4.
U. Schlöder H. Engler U. Schünemann R. Grimm M. Weidemüller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):331-340
We investigate collisional properties of lithium and cesium which are simultaneously confined in a combined magneto-optical
trap. Trap-loss collisions between the two species are comprehensively studied. Different inelastic collision channels are
identified, and inter-species rate coefficients as well as cross-sections are determined. It is found that loss rates are
independent of the optical excitation of Li, as a consequence of the repulsive Li*-Cs interaction. Li and Cs loss by inelastic inter-species collisions can completely be attributed to processes involving
optically excited cesium (fine-structure changing collisions and radiative escape). By lowering the trap depth for Li, an
additional loss channel of Li is observed which results from ground-state Li-Cs collisions changing the hyperfine state of
cesium.
Received 28 December 1998 and Received in final form 16 February 1999 相似文献
5.
A. Fioretti C. Amiot C.M. Dion O. Dulieu M. Mazzoni G. Smirne C. Gabbanini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):189-198
We report the detailed analysis of translationally cold rubidium molecule formation through photoassociation. Cold molecules
are formed after spontaneous decay of photoexcited molecules from a laser cooled atomic sample, and are detected by selective
mass spectroscopy after two-photon ionization into Rb
2
+
ions. A spectroscopic study of the 0
g
-
(5
S
+ 5
P
3/2
) pure long-range state of 87Rb2 is performed by detecting the ion yield as a function of the photoassociation laser frequency; the spectral data are theoretically
analyzed within the semiclassical RKR approach. Molecular ionization is resonantly enhanced through either the 2
3
Π
g
or the 2
3
Σ
+
g
intermediate molecular states. Some vibrational levels of the latter electronic state are observed and assigned here for
the first time. Finally, cold molecules formation rates are calculated and compared to the experimentally measured ones, and
the vibrational distribution of the formed molecules in the a
3
Σ
+
u
ground triplet state is discussed.
Received 18 January 2001 and Received in final form 10 April 2001 相似文献
6.
M.-L. Almazor O. Dulieu F. Masnou-Seeuws R. Beuc G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):355-363
We propose a new possibility to form ultracold molecules, via photoassociation of a pair of cold atoms into vibrational levels of the external well of an excited electronic state located
at intermediate interatomic distance ( ≈ 20 Bohr radii), and embedded in the dissociation continuum above its dissociation
limit. The existence of such a well is demonstrated by conventional free-free absorption spectroscopy at thermal energies.
Estimation for cold atom photoassociation and cold molecule formation rates are obtained within a perturbative approach [Drag
et al., IEEE J. Quant. Electr. 36, 1378 (2000)], and are found observable for usual conditions of photoassociation experiments.
Received 1st March 2001 相似文献
7.
Ch. Lisdat O. Dulieu H. Knöckel E. Tiemann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):319-328
We present a new determination of the potential curves and interactions of the coupled electronic states A
1
Σ
+
u
and b
3
Π
u
of the potassium dimer, based on new laser spectroscopy measurements within a molecular beam, combined with data available
in the literature. We used a new global deperturbation approach, involving the Fourier Grid Hamiltonian method for energy
level calculation. A standard deviation of 1.2 is obtained corresponding to a variance of 7.5×10
-3
cm-1, representing a significant improvement compared to the standard deviation of 4 yielded by the traditional local deperturbation
approach.
Received 12 June 2001 and Received in final form 3 September 2001 相似文献
8.
F. Pereira Dos Santos F. Perales J. Léonard A. Sinatra Junmin Wang F. Saverio Pavone E. Rasel C.S. Unnikrishnan M. Leduc 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):15-22
We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute
rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities,
by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state
( 23
P
2) and metastable state ( 23
S
1) populations is also investigated. From these results we infer a rather uniform rate constant K
sp = (1±0.4)×10-7 cm3/s.
Received 8 September 2000 and Received in final form 19 December 2000 相似文献
9.
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
10.
H.C. Mastwijk M. van Rijnbach J.W. Thomsen P. van der Straten A. Niehaus 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(2):131-137
This paper presents an experimental investigation of cold collisions between metastable helium atoms in an optical trap at
1 mK. Penning (PI) and associative (AI) ionization reactions are distinguished using a mass spectrometer and studied under
influence of near resonant laser light. Dramatic enhancement, by more than a factor 15, of the ion rate is observed when the
laser is tuned close to resonance. Experimental findings are well-described, on an absolute scale, by model predictions.
Received: 9 February 1998 / Revised: 4 May 1998 / Accepted: 14 May 1998 相似文献
11.
V. Wippel C. Binder L. Windholz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):101-104
In a magneto-optical trap (MOT) we are able to simultaneously trap and cool 7Li and Na. We investigated the loading behavior of the cloud of Li atoms in presence of the overlapped cloud of cold Na atoms,
and, by blocking the weak repumping beam for Na, compared it with the loading curve for Li atoms only. Out of these loading
curves we calculated the collision cross-section of Na on Li to be 10-11 cm
3
/s.
Received 11 January 2002 / Received in final form 5 April 2002 Published online 24 September 2002 相似文献
12.
13.
G. Modugno G. Roati M. Inguscio M.S. Santos G.D. Telles L.G. Marcassa V.S. Bagnato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):409-413
We report a comparative investigation of trap loss rates in a magneto-optical trap for two potassium isotopes, 39K and 40K, as a function of trap light intensity. The isotopes present a quite similar behavior for the loss rates at high intensities,
and a sudden increase of the loss rates at low intensities is present in both cases. While for 39K such increase can be explained assuming that the major contribution to the losses comes from hyperfine changing collisions,
a different loss mechanism must be considered for 40K, which has an inverted ground state hyperfine structure. The experimental results of both isotopes are well reproduced by
an alternative model based on radiative escape as the dominant loss mechanism.
Received 1st May 2002 / Received in final form 19 October 2002 Published online 4 March 2003
RID="a"
ID="a"Alternative address: Dipartimento di Fisica, Universitá di Trento, 38050 Povo (Tn), Italy.
RID="b"
ID="b"e-mail: marcassa@if.sc.usp.br 相似文献
14.
J. S. Bakos G. P. Djotyan P. N. Ignácz M. Á. Kedves M. Serényi Zs. Sörlei J. Szigeti Z. Tóth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):141-149
The displacement of Rb atoms in a magneto-optical trap (MOT) caused by the force of a finite time series of counter-propagating
frequency modulated light pulse pairs is measured as a function of the chirp of the pulses. The frequency modulated light
pulses induced 85Rb 52S1/2 F=3 ↔ 85Rb 52P3/2 F'=2, 3, 4 excitation and de-excitation of the atoms. The result of this excitation
de-excitation process is a force causing the acceleration and, consequently, the displacement of the maximum of the spatial
distribution of the trap atoms. The time dependence of the populations of the levels of the atom are calculated — including
also the 85Rb 52S1/2 F=2 and F'=1 states — as
the result of the interaction with the finite train of counter propagating frequency modulated light pulses by the solution
of the Bloch equations. As the result of the measurement the interval of the chirp of the frequency modulated light of given
intensity where the transitions take place, are determined. The results of the experiment and the expectation on the basis
of model calculations are in qualitative agreement. 相似文献
15.
G. Werth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):121-124
Spectroscopic experiments in static or dynamic ion traps have produced results of extremely high precision. They have been,
however, performed mainly on systems with simple electronic level schemes as available in singly charged ions of the earth-alkaline
elements. In this contribution the most complex system investigated so far, Eu+, is used as example to discuss the possibility of spectroscopy on superheavy elements in traps. 相似文献
16.
As it is known [1] an intense laser field can induce atom-atom interaction according to a dipole-dipole R
–3 law. Such an interaction depends on the angle between light polarization and interatomic vector-position R. This angular dependence may produce an anisotropy in the spatial density distribution of the confined sample of cold atoms. We develop the main relations and apply them to the case of an atomic cloud of cold trapped neutral atoms with the density higher than or of the order of –3, where is the wavelength of light. The results presented here show the effect of such an interaction in a density regime of high experimental interest. 相似文献
17.
H. Pu T. Cai N.P. Bigelow 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):269-278
We present a semi-classical theory of the light pressure force for atoms interacting with a two-dimensional laser field. Unlike
previous 2D theory, ours is valid for general atomic level and laser field configurations. We show that striking new features
appear in the velocity-dependent force arising from the multi-dimensionality. Finally, we describe in detail the novel numerical
technique used in the calculation.
Received 4 December 1998 and Received in final form 13 February 1999 相似文献
18.
M. Kajita A. V. Avdeenkov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):499-504
The collisions between linear polar molecules, trapped in
a microwave field with circular polarization, are theoretically
analyzed. We demonstrate that the collisional dynamics is mostly
controlled by two ratios ν/B and x=μ0E0/ħ
B (ν is the microwave frequency, B is the molecular
rotational constant, μ0 is the dipole moment, and E0 is
the electric field amplitude). We discuss the dependence of collision
cross sections on these ratios in order to find an advantageous
condition for evaporative cooling. 相似文献
19.
J. Jersblad H. Ellmann L. Sanchez-Palencia A. Kastberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):333-339
We present a direct measurement of velocity distributions in two dimensions by using an absorption imaging technique in a
3D near resonant optical lattice. The results show a clear difference in the velocity distributions for the different directions.
The experimental results are compared with a numerical 3D semi-classical Monte-Carlo simulation. The numerical simulations
are in good qualitative agreement with the experimental results.
Received 3 September 2002 / Received in final form 25 October 2002 Published online 11 February 2003 相似文献
20.
C. Triché P. Verkerk G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):225-228
We present an experimental study of the kinetic temperature of cesium atoms interacting with laser beams tuned on the blue
side of the transition. In the case of a three-dimensional four-beam molasses, temperatures as low as 800 nK were found. These low temperatures
are compatible with a good capture efficiency. The influence of other hyperfine transitions on the temperature is significant.
In the presence of a static magnetic field (antidot lattices), the temperatures are slightly higher but show a much weaker
dependence on the other hyperfine transitions.
Received: 14 May 1998 / Received in final form: 16 October 1998 / Accepted: 2 November 1998 相似文献