Ph. D. Defense

1
Ph. D. Defense

• Committee
• Chair J. H. Edgar
• Advisor B. D. DePaola
• Member C. L. Cocke
• Member C. D. Lin
• Member P. M. A. Sherwood
• Presenter Hai T. Nguyen

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MOTRIMS Magneto-Optical Trap Recoil Ion Momentum
Spectroscopy

• Hai Nguyen, Richard Brédy, Xavier Fléchard,
• Alina Gearba, How Camp, Takaaki Awata,
• Johnathan Sabah, Kyle Wilson, and Brett DePaola.

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OUTLINE

• Reviews of Cold Target Recoil Ion Momentum
  Spectroscopy
• Motivation
• Experimental Setup
• Results
• Conclusion and Outlook

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COLTRIMS Principles

• Cold Target Recoil Ion Momentum Spectroscopy is a
  technique in which information about the
  collision is obtained through the measurement of
  the momentum transferred to the ionized target
  (atom/molecule).

p
P
p
q
p
P
p
r
p
r -
r
Q energy defect ? Scattering angle (Lab
frame) Prll , Pr? parallel and perpendicular
recoil momentum components PP , PP projectile
momentum before and after the collision Vp
projectile velocity nc number of transferred
electrons
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COLTRIMS Pros Cons

• Pros
• This technique allows kinematically complete
  experiments.
• The good resolution in the measured longitudinal
  recoil ion momentum allows accurate determination
  of the inelasticity in the collision and
  therefore identification of the different
  collision channels by their different Q-values.
• Cons
• Ultimately, in COLTRIMS, the resolution is
  limited by the temperature of the target (gt100
  mK) traditionally delivered by a supersonic jet.
• Problematic for collisions with excited target.

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MOTIVATION

• Collisions with excited target ( 20).
• Resolution is no longer limited by target
  temperatures ( 130mK).
• Cross-section measurements provide rigorous test
  for theory.

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EXPERIMENTAL SETUP
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EXPERIMENTAL RESULTS

• Results Obtained
• Energy dependent Cs Rb (5l), l s and p
• Energy dependent Na Rb (5 l), l s and p
• MOTRIMS probes MOT excited state fractions
• Systems with energetically degenerate channels
  (Dual beam method)
• Li Rb
• K Rb
• Rb Rb

• Results will be shown for
• 7 keV Na Rb (5l), l s and p
• Na Rb (5l) compare with theory
• MOT excited state populations
• Rb Rb(5l), l s and p

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RESULTS7 keV Na Rb (5l), l s and p
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RESULTS7 keV Na Rb (5l), l s and p
Laser off
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MOTRIMS as a probe 7 keV Na Rb (5l), l s
and p
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RESULTS7 keV Na Rb (5l), l s and p
Rb(5s) to final state Relative cross sections (5s)
3s 0.19 0.01
3p 0.78 0.01
3d 0.03 0.01
Rb (5p) to final state Relative cross sections (5p)
3p 0.78 0.02
4s 0.07 0.01
3d 0.11 0.02
4p 0.03 0.01
5s 0.00 0.01
4d 0.01 0.01
7 keV Relative cross sections
sp/ss 2.75 0.01
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RESULTS7 keV Na Rb (5l), l s and p
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RESULTS7 keV Na Rb (5l), l s and p
Compared to calculation
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ENERGY-DEPENDENT RESULTSCompared to calculation
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ENERGY-DEPENDENT RESULTS Compared to calculation
5s-3p
5p-3p
(keV mrad)
(keV mrad)
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MOTRIMS as a probe7 keV Na Rb (5l), l s and
p
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MOTRIMS as a probe 7 keV Na Rb (5l), l s
and p
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MOTRIMS as a probe 7 keV Na Rb (5l), l s
and p
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MOTRIMS as a probe7 keV Na Rb (5l), l s and
p
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Other Collision System Difficulty
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RESULTS7 keV Rb Rb (5l), l s and p
s5s-5p/s5p-5s 2.95 0.05
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RESULTS7 keV Rb Rb (5l), l s and p
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RESULTS7 keV Rb Rb (5l), l s and p
s5s-5p/s5p-5s 2.95 0.05
DCS for resonant channels are more forwardly
peaked
5s-5s Oscillatory Structure 5p-5p No Oscillatory
Structure
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SUMMARY

• Simultaneous measurements of excited state
  fraction and relative cross sections.
• Kinematically complete collisions study for
  alkali ion trapped atoms including
  energetically degenerate systems.
• MOTRIMS is a powerful tool for ion-atom
  collisions.
• Using MOTRIMS as a probe at MOT dynamics under
  some perturbation.

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THANKS

• Committee Members
• MOTRIMS Group
• JRML Support Staff
• Kevin Carnes, Scott Chainey, Charles Fehrenbach,
  Bob Geering, Bob Krause, Vince Needham, Al
  Rankin, Carol Regehr, and Mike Wells.

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Questions Answers

• Cooling and Trapping
• Optics Layouts
• Experimental Setup
• Analysis
• Excited State Formula?
• Others Systems

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SIMPLE OPTICS LAYOUT
QA
29
SIMPLE OPTICS LAYOUT
QA
PBS
l /2
l /4
Mirror
Mirror
From AOM
l /4
l /2
l /4
Mirror
PBS
l /4
TRAPPING OPTICS
l /4
Mirror
Mirror
l /4
Mirror
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Projected TOF
QA
31
RESULTS7 keV Na Rb (5s, 5p)
QA
32
Cooling and Trapping
QA
B
?
?-
Rb
z
VZ
Optical frequency
m 1
m 0
j1
?
m -1
?
?-
?LASER
?m 1
?m -1
z
j 0
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RESULTS7 keV Li Rb (5l), l s and p
QA
34
RESULTS7 keV Li Rb (5l), l s and p
QA
35
Multi-Projectile Source
QA
36
Probe 7 keV Na Rb (5l)
QA
Known
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7 keV Li Rb (5l)
QA
Known
Results
38
Cross Sections 7 keV Li Rb
QA
Waiting for TC-AOCC results
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7 keV Li Rb Scattering Angle Information
QA
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7 keV Li Rb Scattering Angle Information
QA

• Grouped scattering angle information are hard to
  extrapolate (Rb Rb).
• Theoretical Comparison not trustworthy.
• Using a weighted method to deduce individual
  channel scattering angle information.

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7 keV Li Rb Scattering Angle Information
QA
Laser on
Laser off
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7 keV Li Rb Scattering Angle Information
QA
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RESULTS6 keV Cs Rb (5l), l s and p
QA
44
RESULTS6 keV Cs Rb (5l), l s and p
QA
45
QA
SINGLE CAPTURE IN 6 keV Cs Rb (5l), l s
and p

• Recoil ion PSD image

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RESULTSEnergy dependent Cs Rb (5l), l s and
p
QA
47
Excited State Fraction Formula?
QA
48
So, Whats the Problem!?
So, Whats the Problem!?
QA
49
So, Whats the Problem!?
So, Whats the Problem!?
QA
Beam Symmetry?
I2 0.45 mW / cm2
B-Field Gradient?
I1 0.50 mW / cm2
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Preliminary Results
Preliminary Results
QA