Collisional loss rate measurement of Cesium atoms in MOT

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Collisional loss rate measurement of Cesium atoms
in MOT
Speaker Wang guiping Date December 25
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Outline

• Introduction
• Experiment setup
• Experimental results and analysis
• Conclusion

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Outline

• Introduction
• Experiment setup
• Experimental results and analysis
• Conclusion

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Cold and ultracold collisions occupy a strategic
position at the intersection of several powerful
themes of current research in chemical physics,
in atomic, molecular, and optical physics, and
even in condensed matter. The nature of these
collisions bear critically in optical
manipulation of inelastic and reactive processes,
precision measurement of molecular and atomic
properties, matter-wave coherences and
quantum-statistical condensated of dilute, weakly
interacting atoms.
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An inelastic collision, which released energy,
is a bad collision , atoms gain in kinetic
escape the trap.
Collisions processes are thus a limiting factor
for attaining high densities and low temperatures
in all traps.
Determination the collision rate coefficient
Trapping laser intensity dependence
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Outline

• Introduction
• Experiment setup
• Experimental results and analysis
• Conclusion

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Our experimental parameters
Background pressure in glass MOT 110-7
Pa Magnetic field grads 15Gauss/cm Trap laser
power 4mW Diameter of trap lasers
10mm Repumping laser power 5mW Diameter of
repumping lasers 15mm Dimension of cold atoms
cloud 0.8mm Number of the trapped atoms
1107 Density of cold atoms cloud 41010
atoms/cm3 Temperature of cold atoms 100µK
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Outline

• Introduction
• Experiment setup
• Experimental results and analysis
• Conclusion

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The time dependence of the number of atoms
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Radiation trapping

• If the density becomes very high in a MOT, there
  is a larger probability that a scattered photon
  will be re-absorbed by an other atom.
• This will result in a repulsive force between
  the two atoms.
• This will limit the maximum density in a MOT.
• Eventually, the density becomes constant, and
  continued filling only leads to a growth of the
  cloud.

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L.Marcassa .et al.,Rhys.Rev.A.47,6
The slope equal to
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Gallagher-Pritchard model
radiative escape fine-structure-changing
collision
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Outline

• Introduction
• Experiment setup
• Experimental results and analysis
• Conclusion

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• We measure the collision loss rate for ultracold
  cesium atoms in MOT as a function of the trapping
  laser intensity.
• We interpreted the results with collision theory.
  

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Thank you