Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Laser Physics

Revisiting the capture velocity of a cesium magneto-optical trap: model, simulation and experiment

Muhammad Anwar, Daniel Varela Magalhães, Stella Müller, Muhammad Hamza Faisal, Muhammad Yasir Nawaz, Mushtaq Ahmed

Published Oct 7, 2014• 4 citations
Publisher

Abstract

In this work, we have explored ab initio the capture process in a magneto-optical trap by theory, simulation and experiment. We measured the capture velocity vc of a cesium vapor cell magneto-optical trap (VCMOT) from its capture rate R and developed an exact model for the capture rate of a VCMOT in terms of its capture velocity, background density and trap laser beam diameter. We measured the capture velocity of a cesium VCMOT for various trap laser intensities and magnetic field gradients. We observed that the capture velocity is a damping force as well as a restoring force phenomenon. We supported our findings by performing simulations for single atom trajectories in a 1D cesium MOT. Finally, we concluded that two MOTs can have the same capture velocities but very different capture rates, thereby revealing that these are two fundamentally different characteristics of the MOT.

DOI
10.1088/1054-660x/24/12/125502

Related papers

Magneto-optical trap loading rate dependence on trap depth and vapor density

Magnus A. Haw, N. Evetts, Will Gunton +3 more

We study the dependence of the particle loading rate of a rubidium vapor cell magneto-optic trap (MOT). Using a trap depth determination of the MOT that relies on measurements of loss rates during optical excitation of colliding atoms to a repulsive molecular state, we experimentally determine the MOT escape velocity and show that the loading rate scales with escape velocity to the fourth power, or, equivalently, with the square of the trap depth. We also demonstrate that the loading rate is directly proportional to the background rubidium density. We thus experimentally confirm the loading rate model used in the literature since the invention of the MOT. In addition to confirming this long-standing conjecture, we show that the loading rate dependence can be used to reliably infer the trap depth and to tune the relative depth of a MOT (i.e., capture and escape velocities) when the background density is held fixed. The measurements have allowed an experimental determination of the relationship between capture and escape velocities in our MOTs of vc=1.29(0.12)ve.

Journal of the Optical Society of America B•Feb 28, 2012•20 citations

Magneto-optical trap loaded from a low-velocity intense source

Chang Yong Park, Myung Sim Jun, D. Cho

With a vapor-cell magneto-optical trap (VCMOT) atoms are trapped directly from the equilibrium vapor at room temperature without the complication of a precooling stage. The background vapor, however, can also be a source of energetic atoms hitting and ejecting those atoms already trapped. The background collision limits trap confinement time /spl tau/ and consequently the total number N of atoms trapped in a VCMOT. In order to have large /spl tau/ and N without losing the convenience and simplicity of a VCMOT, double MOT systems were built. In such a system there is a VCMOT with a usual background vapor pressure, and connected to it is another MOT without the vapor. The VCMOT captures atoms and transfers them to the second MOT through a long tube. The tube provides the constriction to maintain the pressure difference between the two MOT chambers. For the second MOT there is a steady supply of slow atoms without the complication of the background vapor, and it can hold a large number of atoms for a long time. Such systems were successfully used for a Bose Einstein condensation experiment and to study cold collisions.

Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR)•Jan 20, 2003•0 citations

The capture process in spherical magneto-optical traps: experiment and 1D magnetic field models

N Sagna, G. Dudle, P. Thomann

The influence of the magnetic field gradient on the number of Cs atoms captured in a three-dimensional magneto-optical trap is investigated both theoretically and experimentally. Two one-dimensional models of the capture process are proposed, which differ only by the nature of the assumptions on the effect of Zeeman optical pumping. Transverse cooling beams are accounted for by a mere modification of the scattering rate. Comparison with experiment shows that the number of trapped atoms versus laser detuning, laser intensity, laser beam diameter and magnetic field gradient is best predicted by a model including all Zeeman substates of the Cs atoms. Quantitative agreement is within a factor of three in most cases of interest.

Journal of Physics B Atomic Molecular and Optical Physics•Aug 14, 1995•9 citations

Magneto-optical trap and its application to ultra-cold atom collision studies

Yanyang Xiao

We have successfully trapped $\\sp7$Li in a vapor cell magneto-optical trap (MOT). The trap is studied in detail and the parameters are measured from the experiment. The trapping mechanism has been understood in terms of the radiation force and a simple one dimensional model is used in interpreting and predicting the experimental results. The cold-cold atom collision rate coefficient is measured in a beam MOT. The two collision mechanisms, fine structure changing and radiative escape, are discussed in a molecular picture. One of the channels, the fine structure changing channel, can be turned on and off by the experimental conditions, namely the laser intensity in this experiment. The rate coefficient for each mechanism has been determined from the experiment.

•Jan 1, 1994•0 citations

Analysis of a vapor cell magneto optical trap for sodium atoms based on a two level. Doppler theory

D. M. B. P. Milori, M. T. de Araújo, I. Guedes +2 more

We present an experimental study to characterize a sodium vapor-cell magneto-optical trap (VCMOT) in terms of the number and density of trapped atoms, loading rate and load-ing time. We have investigated how these quantities change with the vapor temperature, magnetic- eld gradient and laser intensity. The results obtained are explained with a sim-ple model that employs the Doppler theory. Good agreement is obtained for most of the experimental data. Investigations on the size of the cloud as a function of the trap external parameters are also carried out. The information MOT in order to obtain the maximum presented here is useful in optimizing the number and density of trapped atoms, normally required for experiments of atomic collisions and Bose-Einstein condensation. I.

Brazilian Journal of Physics•Jun 1, 1997•9 citations

Velocity-tunable magneto-optical-trap-based cold Cs atomic beam

He Wang, Walter F. Buell

We report our observation and investigation of a magneto-optical-trap- (MOT)-based low-velocity Cs atomic beam for atomic clock applications. We generated a continuous Cs atomic beam from a vapor-cell MOT of Cs atoms by forming a leak tunnel along one of the trapping laser beams. The mean velocity of the cold Cs beam is measured by the time-of-flight technique to be 7.3 m/s with a velocity spread of 1 m/s under nominal experimental conditions. By adjusting the MOT parameters, we are able to tune the Cs beam velocity from 5 to 8.5 m/s while the velocity spread remains at 1 m/s. The Cs beam has an instantaneous atomic flux of 3.6× 1010 atoms/s when operated in pulsed mode and an estimated continuous beam flux of 2×108 atoms/s. The acceleration kinetics of the Cs beam in the acceleration region is analyzed and simulated. Our theoretical model reveals that the MOT inhomogeneous magnetic field and the varying Doppler shift along the atomic beam propagation play an important role in the determination of the final velocity of the Cs atomic beam. Our numerical results of the atomic beam velocity on MOT parameters agree well with the measurements.

Journal of the Optical Society of America B•Oct 1, 2003•17 citations
In this work, we have explored ab initio the capture process in a magneto-optical trap by theory, simulation and experiment. We measured the capture velocity vc of a cesium vapor cell magneto-optical trap (VCMOT) from its capture rate R and developed an exact model for the capture rate of a VCMOT in terms of its capture velocity, background density and trap laser beam diameter. We measured the capture velocity of a cesium VCMOT for various trap laser intensities and magnetic field gradients. We observed that the capture velocity is a damping force as well as a restoring force phenomenon. We supported our findings by performing simulations for single atom trajectories in a 1D cesium MOT. Finally, we concluded that two MOTs can have the same capture velocities but very different capture rates, thereby revealing that these are two fundamentally different characteristics of the MOT.
We study the dependence of the particle loading rate of a rubidium vapor cell magneto-optic trap (MOT). Using a trap depth determination of the MOT that relies on measurements of loss rates during optical excitation of colliding atoms to a repulsive molecular state, we experimentally determine the MOT escape velocity and show that the loading rate scales with escape velocity to the fourth power, or, equivalently, with the square of the trap depth. We also demonstrate that the loading rate is directly proportional to the background rubidium density. We thus experimentally confirm the loading rate model used in the literature since the invention of the MOT. In addition to confirming this long-standing conjecture, we show that the loading rate dependence can be used to reliably infer the trap depth and to tune the relative depth of a MOT (i.e., capture and escape velocities) when the background density is held fixed. The measurements have allowed an experimental determination of the relationship between capture and escape velocities in our MOTs of vc=1.29(0.12)ve.
With a vapor-cell magneto-optical trap (VCMOT) atoms are trapped directly from the equilibrium vapor at room temperature without the complication of a precooling stage. The background vapor, however, can also be a source of energetic atoms hitting and ejecting those atoms already trapped. The background collision limits trap confinement time /spl tau/ and consequently the total number N of atoms trapped in a VCMOT. In order to have large /spl tau/ and N without losing the convenience and simplicity of a VCMOT, double MOT systems were built. In such a system there is a VCMOT with a usual background vapor pressure, and connected to it is another MOT without the vapor. The VCMOT captures atoms and transfers them to the second MOT through a long tube. The tube provides the constriction to maintain the pressure difference between the two MOT chambers. For the second MOT there is a steady supply of slow atoms without the complication of the background vapor, and it can hold a large number of atoms for a long time. Such systems were successfully used for a Bose Einstein condensation experiment and to study cold collisions.
The influence of the magnetic field gradient on the number of Cs atoms captured in a three-dimensional magneto-optical trap is investigated both theoretically and experimentally. Two one-dimensional models of the capture process are proposed, which differ only by the nature of the assumptions on the effect of Zeeman optical pumping. Transverse cooling beams are accounted for by a mere modification of the scattering rate. Comparison with experiment shows that the number of trapped atoms versus laser detuning, laser intensity, laser beam diameter and magnetic field gradient is best predicted by a model including all Zeeman substates of the Cs atoms. Quantitative agreement is within a factor of three in most cases of interest.
We have successfully trapped sp7\\sp7sp7Li in a vapor cell magneto-optical trap (MOT). The trap is studied in detail and the parameters are measured from the experiment. The trapping mechanism has been understood in terms of the radiation force and a simple one dimensional model is used in interpreting and predicting the experimental results. The cold-cold atom collision rate coefficient is measured in a beam MOT. The two collision mechanisms, fine structure changing and radiative escape, are discussed in a molecular picture. One of the channels, the fine structure changing channel, can be turned on and off by the experimental conditions, namely the laser intensity in this experiment. The rate coefficient for each mechanism has been determined from the experiment.
We present an experimental study to characterize a sodium vapor-cell magneto-optical trap (VCMOT) in terms of the number and density of trapped atoms, loading rate and load-ing time. We have investigated how these quantities change with the vapor temperature, magnetic- eld gradient and laser intensity. The results obtained are explained with a sim-ple model that employs the Doppler theory. Good agreement is obtained for most of the experimental data. Investigations on the size of the cloud as a function of the trap external parameters are also carried out. The information MOT in order to obtain the maximum presented here is useful in optimizing the number and density of trapped atoms, normally required for experiments of atomic collisions and Bose-Einstein condensation. I.
We report our observation and investigation of a magneto-optical-trap- (MOT)-based low-velocity Cs atomic beam for atomic clock applications. We generated a continuous Cs atomic beam from a vapor-cell MOT of Cs atoms by forming a leak tunnel along one of the trapping laser beams. The mean velocity of the cold Cs beam is measured by the time-of-flight technique to be 7.3 m/s with a velocity spread of 1 m/s under nominal experimental conditions. By adjusting the MOT parameters, we are able to tune the Cs beam velocity from 5 to 8.5 m/s while the velocity spread remains at 1 m/s. The Cs beam has an instantaneous atomic flux of 3.6× 1010 atoms/s when operated in pulsed mode and an estimated continuous beam flux of 2×108 atoms/s. The acceleration kinetics of the Cs beam in the acceleration region is analyzed and simulated. Our theoretical model reveals that the MOT inhomogeneous magnetic field and the varying Doppler shift along the atomic beam propagation play an important role in the determination of the final velocity of the Cs atomic beam. Our numerical results of the atomic beam velocity on MOT parameters agree well with the measurements.