Pr

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2 new very accurate determinations of the s-wave
scattering length in metastable helium
Steven Moal, Maximilien Portier, Julien Dugué,
Christian Buggle, Nassim Zahzam, Michèle Leduc,
Claude Cohen-Tannoudji
séminaire Atomes-froids vendredi 28 octobre 2005
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Study with 1 photon Frequency shifts of
photoassociative spectra
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Principle of experiment
E
0u
S P0
Ev 0 (?,I)
?
Energy
5 ? g
continuum
kBT
S S
?r
v14
R
Interatomic distance
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Principle of experiment
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Experimental result
From comparison with theory Our value a 7.2
0.5 nm
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Study with 2 photons Dark atom-molecule
resonances Mesure of lifetime and position of
v14
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2 photon spectroscopy
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From Autler-Townes to Raman effect
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From Autler-Townes to dark resonance
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From Autler-Townes to dark resonance
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From Autler-Townes to dark resonance
E
0u
S P0
v0
?2
?1
Energy
5 ? g
continuum
kBT
S S
?r -90 MHz
v14
R
Interatomic distance
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From Autler-Townes to dark resonance
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Dark resonance
destructive interference between the absorption
amplitude of photon 1 on the free / bound v0
transition and of photon 2 on the bound v0 /
bound v14 transition
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Mesure of Ev14
no need of the energy of v0
Position of v14 -91.35 0.06 MHz
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Scattering length
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Other results
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Mesure of lifetime ?v14
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Conclusion

• 2 very accurate (and different) measurements
• of the scattering length
• with frequency shift a 7.2 0.5 nm
• with dark resonance a 7.512 0.005 nm
• Creation of exotic molecules of 2 metastables
• with inhibited autoionisation with
• a lifeduration of 0.5 lt ?v14 /2? lt 3 µs

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Soon

• influence of density on ?v14
• a better value for ?v14 with the study of Raman
  signal
• in fonction of temperature
• in fonction of the detuning
• position and width of v14
• in the potential S-S (M0)
• study of the 2 photons signal
• during the transition
• thermal cloud / BEC

E
S-P0
v 0
?2 , ?
?1 , ?-
S-S MJ2
v14
2µB0
S-S MJ0
v14
R
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Other experiments
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Other experiments

• dip width around 5 MHz du to
• thermal energy distribution at T150 µK, kBT/h3
  MHz
• intensity of 2nd photon kept high

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Principle of experiment
0.5 MHz
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Raman effect
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Mesure of PA rate transition ?
?Therm 0 ms
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Black resonance
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séminaire du vendredi 10/06/05
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E
E
0u
S P0
5 ? g
kBT
v0
continuum
?r
S S h ?
v14
R
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