共查询到20条相似文献,搜索用时 31 毫秒
1.
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》2006,37(1):59-66
The spatial displacement of the 85Rb atoms in a
Magneto-Optical Trap (MOT) under the influence of series of frequency
modulated light pulse pairs propagating opposite to each other is measured
as a function of the time elapsed after the start of the pulse train, and
compared with the results of simulations. Adiabatic excitation and
consecutive de-excitation take place between the ground
52S1/2 (F=3) and the 52P3/2 (F'=2, 3, 4) excited levels as the result of
the interaction. The displacement of the 85Rb atoms is calculated as
the solution of simple equation of motion where the expelling force is that
arising from the action of the frequency modulated light pulses. The
restoring and friction forces of the MOT are taken into account also. The
system of Bloch equations for the density matrix elements is solved
numerically for transitions between six working hyperfine levels of the atom
interacting with the sequence of the frequency modulated laser pulses.
According to these simulations, the momentum transferred by one pulse pair
is always smaller than the expected 2ħk, (1) where ħ is the Plank constant and
k=2π/λ where λ is the wavelength, (2) having a maximum
value in a restricted region of variation of the laser pulse peak intensity
and the chirp. 相似文献
2.
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
3.
E. Rasel F. Pereira Dos Santos F. Saverio Pavone F. Perales C.S. Unnikrishnan M. Leduc 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):311-316
We report a study of transverse laser cooling on a metastable helium beam using spectrally broadened diode lasers (“white
light") to increase its flux. For this purpose, beam profile and atomic flux versus laser power and other parameters have been characterized. We have performed experiments to compare this technique with other
transverse cooling methods using monochromatic light. Best results are obtained with a “ziz-zag" configuration using “white
light".
Received 21 December 1998 and Received in final form 27 May 1999 相似文献
4.
G. Labeyrie A. Browaeys W. Rooijakkers D. Voelker J. Grosperrin B. Wanner C.I. Westbrook A. Aspect 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):341-350
We have constructed a magneto-optical funnel for He atoms and studied its properties using a laser cooled, highly mono-energetic
atomic beam. A simple model of its action allows us to quantitatively understand the observed spot size and “focal length”.
We show that for a fast beam, the velocity damping coefficient plays an important role in determining the focal length of
the device. The observed spot size is limited mainly by transverse heating processes which impose a transverse velocity spread.
The device also permits easy scanning of the focussed spot.
Received 30 October 1998 and Received in final form 27 January 1999 相似文献
5.
An atom faucet 总被引:3,自引:0,他引:3
W. Wohlleben F. Chevy K. Madison J. Dalibard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):237-244
We present a simple and efficient source of slow atoms. From a background vapour loaded magneto-optical trap (MOT), a thin
laser beam extracts a continuous jet of cold rubidium atoms. The jet that is typical to leaking MOT systems is created without
any optical parts placed inside the vacuum chamber. We also present a simple three dimensional numerical simulation of the
atomic motion in the presence of these multiple saturating laser fields combined with the inhomogeneous magnetic field of
the MOT. At a pressure of P
Rb87 = 10-8 mbar and with a moderate laser power of 10 mW per beam, we generate a flux Φ = 1.3×108 atoms/s with a mean velocity of 14 m/s and a divergence of 10 mrad.
Received 13 January 2001 相似文献
6.
R. Chicireanu Q. Beaufils A. Pouderous B. Laburthe-Tolra É. Maréchal L. Vernac J.-C. Keller O. Gorceix 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):189-195
We report the fast accumulation of a large number of
metastable 52Cr atoms in a mixed trap, formed by the
superposition of a strongly confining optical trap and a quadrupolar
magnetic trap. The steady state is reached after about 400 ms,
providing a cloud of more than one million metastable atoms at a
temperature of about 100 μK, with a peak density of 1018
atoms m-3. We have optimized the loading procedure, and
measured the light shift of the 5D4 state by analyzing how the
trapped atoms respond to a parametric excitation. We compare this
result to a theoretical evaluation based on the available
spectroscopic data for chromium atoms. 相似文献
7.
Reflection of thermal atoms by a pulsed standing wave 总被引:1,自引:0,他引:1
P. Ryytty M. Kaivola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):415-423
Reflection of thermal atoms by a pulsed standing wave with a duration in the nanosecond range is studied. The momentum distribution
of the reflected atoms is determined by calculations based on the adiabatic atom-photon interactions. It is shown that with
a proper choice of the field intensity and the pulse duration the standing-wave pattern functions as a row of independent
atom mirrors. At an optimum choice of the parameter values, the fraction of the elastically reflected atoms is more than 20%.
Furthermore, we show that the pulsed standing-wave mirror can be used to manipulate their final momentum distribution. When
using laser pulses with an intensity of several tens of MW/cm2, tens of thousands of atoms can be reflected by a single laser pulse.
Received 3 December 1999 and Received in final form 25 April 2000 相似文献
8.
Ch. Grain T. Nazarova C. Degenhardt F. Vogt Ch. Lisdat E. Tiemann U. Sterr F. Riehle 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):317-324
We have investigated the influence of narrow-line laser cooling on the loading of Ca atoms into optical dipole traps.
To describe the narrow-line cooling of alkaline-earth atoms in combination with optical dipole trapping, we have developed
a model
that takes into account the light shifts of the cooling transition in three dimensions.
The model is compared with two experimental realizations of optical dipole traps for calcium at the wavelengths 514 nm and
10.6 μm. 相似文献
9.
C.M. Dion A. Keller O. Atabek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):249-255
Using a rigid-rotor model, we study the orientation dynamics of polar diatomic molecules excited by experimentally available
half-cycle pulses. The results of the numerical solution of the time-dependent Schr?dinger equation are compared to those
of an approximate “sudden-impact” impulsive model neglecting the molecular rotation during the pulse. We show that efficient
orientation is achieved during time periods of several picoseconds for LiCl. For short pulses, where the kicked molecule model
is valid, orientation turns out to be mainly sensitive to the time-integrated field amplitude and not the shape or rise time
of the pulse.
Received 16 August 2000 and Received in final form 4 December 2000 相似文献
10.
11.
M. Gangl H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):29-40
We develop quantum models for the combined external and internal motion of atoms in a strongly coupled driven cavity mode
including the transverse degrees of freedom. Using a simplified Gaussian mode function we determine the parameter regimes
and prospects of 3D cooling and confinement of one or two atoms in the cavity field. Analysing the field dynamics for slow
atoms traversing the cavity, we show that the spectrum of the transmitted and spontaneously scattered light contains ample
information on the motional dynamics of the atom and can be nicely used to investigate the cooling properties of the system.
Including several atoms in the dynamics we show how motional correlations build up by the common interaction with the cavity
field. This can be looked upon as collisions at far distance and can be monitored via the transmitted field dynamics.
Received 5 March 1999 and Received in final form 4 May 1999 相似文献
12.
C. Champenois M. Büchner J. Vigué 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(3):363-374
Several three-grating Mach-Zehnder atomic interferometers have been built and operated in recent years but no general theory
of the contrast of the fringes produced by these apparatus is available. The purpose of this paper is to develop this theory,
based on the Fresnel-Kirchoff approximate treatment of diffraction. Such a theory has been developed by Turchette et al. [JOSA B 9, 1601 (1992)] but because the necessary multiple integrals were evaluated in a purely numerical way, this treatment was not
fully general. We show here how to reduce the computation by analytic means and we are thus able to calculate the contrast
with a modest numerical effort. Moreover, we get a simple insight of the contrast reduction related to several defects of
a real apparatus. We apply our calculations to existing interferometers as well as to an apparatus working with lithium which
is under construction in our laboratory.
Received: 24 April 1998 / Revised: 25 October 1998 / Accepted: 11 December 1998 相似文献
13.
P. Sjölund S. J.H. Petra C. M. Dion H. Hagman S. Jonsell A. Kastberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):381-388
We present here a detailed study of the behaviour of a three dimensional Brownian motor based on cold atoms in a double optical
lattice [P. Sj?lund et al., Phys. Rev. Lett. 96, 190602 (2006)]. This includes both experiments and numerical simulations of a Brownian particle. The potentials used are
spatially and temporally symmetric, but combined spatiotemporal symmetry is broken by phase shifts and asymmetric transfer
rates between potentials. The diffusion of atoms in the optical lattices is rectified and controlled both in direction and
speed along three dimensions. We explore a large range of experimental parameters, where irradiances and detunings of the
optical lattice lights are varied within the dissipative regime. Induced drift velocities in the order of one atomic recoil
velocity have been achieved. 相似文献
14.
G. Reinaudi Z. Wang A. Couvert T. Lahaye D. Guéry-Odelin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):405-410
A fast packet of cold atoms is coupled into a magnetic
guide and subsequently slowed down by reflection on a magnetic
potential barrier (`mirror') moving along the guide. A detailed
characterization of the resulting decelerated packet is performed.
We show also how this technique can be used to generate a
continuous and intense flux of slow, magnetically guided atoms. 相似文献
15.
L. Sanchez-Palencia P. Horak G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):353-364
We numerically study the spatial diffusion of an atomic cloud experiencing Sisyphus cooling in a three-dimensional linlin optical lattice in a broad range of lattice parameters. In particular, we investigate the dependence on the size of the
lattice sites which changes with the angle between the laser beams. We show that the steady-state temperature is largely independent
of the lattice angle, but that the spatial diffusion changes significantly. It is shown that the numerical results fulfill
the Einstein relations of Brownian motion in the jumping regime as well as in the oscillating regime. We finally derive an
effective Brownian motion model from first principles which gives good agreement with the simulations.
Received 8 August 2001 and Received in final form 6 November 2001 相似文献
16.
17.
P. Ryytty M. Kaivola C.G. Aminoff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):369-372
We study the deflection of sodium atoms by a resonantly tuned pulsed standing wave of high field intensity. The effects of
the phase fluctuations of the pulsed laser field on the momentum distribution of the deflected atoms are experimentally determined.
The results are explained using a theoretical model based on the generalized density matrix formalism of two-level atoms.
Received 23 November 1998 and Received in final form 27 January 1999 相似文献
18.
P. Domokos T. Kiss J. Janszky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):49-53
A beam of diatomic molecules scattered off a standing wave laser mode splits according to the rovibrational quantum state
of the molecules. Our numerical calculation shows that single state resolution can be achieved by properly tuned, monochromatic
light. The proposed scheme allows for selecting non-vibrating and non-rotating molecules from a thermal beam, implementing
a laser Maxwell's demon to prepare a rovibrationally cold molecular ensemble.
Received 23 August 2000 and Received in final form 17 November 2000 相似文献
19.
20.
P. Cren C.F. Roos A. Aclan J. Dalibard D. Guéry-Odelin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):107-116
We demonstrate experimentally the continuous and pulsed loading of a slow and cold atomic beam into a magnetic guide. The
slow beam is produced using a vapor loaded laser trap, which ensures two-dimensional magneto-optical trapping, as well as
cooling by a moving molasses along the third direction. It provides a continuous flux larger than 109 atoms/s with an adjustable mean velocity ranging from 0.3 to 3 m/s, and with longitudinal and transverse temperatures smaller
than 100 μK. Up to 3×108 atoms/s are injected into the magnetic guide and subsequently guided over a distance of 40 cm.
Received 19 February 2002 Published online 28 June 2002 相似文献