NNV NNV - - AMO meeting, AMO meeting, Lunteren Lunteren 11.11.2005 11.11.2005 Laser Centre Vrije Universiteit, Amsterdam Bose Bose - - Fermi mixtures of Fermi mixtures of metastable metastable helium helium Andrey Andrey Tychkov Tychkov Tom Tom Jeltes Jeltes John M John M c c Namara Namara Wim Wim Vassen Vassen Wim Wim Hogervorst Hogervorst BEC of BEC of 4 4 He*: He*: January January 27, 2005 27, 2005 DFG of DFG of 3 3 He*: November 18, 2005 He*: November 18, 2005 Modern Trends in Atomic Physics II Modern Trends in Atomic Physics II June 2 June 2 nd nd , Gothenburg, Sweden , Gothenburg, Sweden
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NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
BoseBose--Fermi mixtures of Fermi mixtures of metastablemetastable helium helium
AndreyAndrey Tychkov Tychkov
Tom Tom JeltesJeltes
John MJohn MccNamaraNamara
WimWim VassenVassen
WimWim HogervorstHogervorst
BEC of BEC of 44He*: He*: JanuaryJanuary 27, 200527, 2005DFG of DFG of 33He*: November 18, 2005He*: November 18, 2005
Modern Trends in Atomic Physics IIModern Trends in Atomic Physics IIJune 2June 2ndnd , Gothenburg, Sweden, Gothenburg, Sweden
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
Group leader : Prof. Group leader : Prof. WimWim UbachsUbachsResearch themes: molecular physics, XUV spectroscopyResearch themes: molecular physics, XUV spectroscopy
- search for possible variation of µµµµ=Mp/me over cosmological time
Staff member: Dr. Staff member: Dr. KjeldKjeld EikemaEikemaResearch: Research: ultrafastultrafast lasers, frequency comb spectroscopylasers, frequency comb spectroscopy
Staff member: Dr. Staff member: Dr. WimWim VassenVassenResearch: laser cooling & trappingResearch: laser cooling & trapping
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
XUV-laser setup with PDA: ∆νννν ~ 250 MHz
HH22 spectroscopy in lab spectroscopy in lab vsvs Quasar dataQuasar data
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
ESO-VLT ChileNew set of more accurate quasar data:Uncertainty claimed: 2 x 10-7 - 1 x 10-6
Ivanchik, Petitjean et al, A&A 440, 45 (2005)
39 lines in Q 0347-383(z = 3.0248992)
37 lines in Q 0405-443(z = 2.5947328)
Q0347-383
and
Various tests performed
-blending with Lyman forest
-kinetics (J-effects)
-calibrations
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
Q0347
Q0405
weighted fit
510)59.044.2(
−×±=
∆
µ
µ
unweighted fit
510)57.001.2(
−×±=
∆
µ
µ
Total set
PRL 96, 151101 (21 april 2006):“Indication of a Cosmological Variation of the Proton-Electron Mass Ratio Based on Laboratory Measurement and Reanalysis of H2 spectra”
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
frequency comb laser
AOM
piezo
pump laser5 W green
Rb atomic clock 10 GHz
Waveformgenerator
BBOPBS
λ/2
λ/2
PBS
APD
holey fiber
PID
PID
temp.
control
10 fs,75 MHz Ti:Sa laser
filter
Oscilloscope
FrequencyCounters
SpectrumAnalyzer
GPS receiver
12 digit accuracydue to Rb-clock + GPS correction
f:2f interferometer
frequency
I
0
f0
fr
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
NN0 0 via via µµµµµµµµ or integralor integral
µµNN00
TT
Method 1:Method 1:
NN0 0 = integral of green = integral of green curve times MCP curve times MCP calibration (20% accuracy)calibration (20% accuracy)
from fit from fit noncondensednoncondensed part:part: TTcc~2 ~2 µK µK and and NNTT
maximum number maximum number deduced: deduced: NN00=1 x 10=1 x 107
7
However: saturation of However: saturation of MCP for NMCP for N00 > 1 x 10> 1 x 1066
NN00 too smalltoo small
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
µµ extracted from width of extracted from width of TOF signal (radial expansion TOF signal (radial expansion only!) gives only!) gives NN00 = = 5 x 105 x 107
7( )
52
015
2
=
ho
hoTF
m
aN
ω
ωµ
h
h
Method 2Method 2 : N: N0 0 via chemical potentialvia chemical potential
µµNN00
TT
However: Absorption imaging However: Absorption imaging reveals anomalous expansion reveals anomalous expansion of the BEC as a result of too of the BEC as a result of too slow trap switchslow trap switch--off: off: stretching in radial direction.stretching in radial direction.
NN00 too largetoo large
lengthscatteringa
potentialchemical
zyxho
−
−
=
µ
ωωωω 3
1.5 x 101.5 x 1077<N<N00< 4 x 10< 4 x 107
7
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
Decay of the condensate:Decay of the condensate:the effect of atomic transferthe effect of atomic transfer
Model :Model :P. Zin, A. Dragan, S. Charzynski, N. Herschbach, P. Tol,W. Hogervorst, W. Vassen, J. Phys. B 36, L149 (2003)
Assumption: Assumption:
BEC + thermal cloud remain in BEC + thermal cloud remain in thermodynamic equilibrium during thermodynamic equilibrium during decaydecay
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
�� Atoms lost from the condensate Atoms lost from the condensate are lost from the trap, or are lost from the trap, or transferred to the thermal cloud. transferred to the thermal cloud.
�� The presence of a thermal cloud The presence of a thermal cloud reduces the lifetime of a BECreduces the lifetime of a BEC
�� In thermal equilibrium transfer In thermal equilibrium transfer has to occur: a condensate atom has to occur: a condensate atom has less energy than a thermal has less energy than a thermal atomatom
�� More complicated equations More complicated equations when also twowhen also two--body (body (ββ) and ) and threethree--body (L) losses are body (L) losses are incorporatedincorporated
When only background gas When only background gas collisions are taken into collisions are taken into acountacount::
Decay of the condensate:Decay of the condensate:the effect of atomic transferthe effect of atomic transfer
+−= TCC NNN
4
11
τ&
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
Decay of the condensate:Decay of the condensate:the effect of atomic transferthe effect of atomic transfer
BEC is detected up to t=75 sBEC is detected up to t=75 s
Estimated loss rate constants:Estimated loss rate constants:ββ=2(1) =2(1) ××1010
--1414cmcm
33/s/s
L=9(3) L=9(3) ××1010--2727
cmcm66/s/s
•• -- quasiquasi--pure BECpure BEC
-- NN00=N=Nth th (t=0)(t=0)
BEC lifetime BEC lifetime
For quasiFor quasi--pure BEC the model gives pure BEC the model gives decay without atomic transferdecay without atomic transfer(upper curve)(upper curve)
BB: Fermi or Bose gas in : Fermi or Bose gas in classical limit classical limit (T>>T(T>>TFF,T,TCC))
CC: Bose gas just above T: Bose gas just above TCC
Check: MaxwellCheck: Maxwell--BoltzmannBoltzmann fits to the wingsfits to the wings
NNVNNV--AMO meeting, AMO meeting, LunterenLunteren 11.11.200511.11.2005Laser Centre Vrije Universiteit, Amsterdam
SummarySummary
�� Large Large 44He* BECHe* BEC�� SofarSofar 2 degenerate 2 degenerate fermionicfermionic species (species (66Li, Li, 4040K); K);
now a third one: now a third one: 33HeHe�� New physics with New physics with 33He* fermions:He* fermions:
–– HanburyHanbury Brown and Brown and TwissTwiss experiment (collaboration LCFIO experiment (collaboration LCFIO OrsayOrsay))–– Phase separationPhase separation–– Search for Search for FeshbachFeshbach resonances: vary scattering lengths?resonances: vary scattering lengths?–– PP--wave Cooper pairingwave Cooper pairing–– Optical latticeOptical lattice–– Suppression of spontaneous emissionSuppression of spontaneous emission–– Metrology: QED, nuclear charge radius Metrology: QED, nuclear charge radius
(2 (2 33SS11 –– 2 2
11SS00 magnetic dipole @1.56 magnetic dipole @1.56 µµm)m)
�� MetastabilityMetastability–– Enhanced detection efficiencyEnhanced detection efficiency–– Access to major density dependent lossesAccess to major density dependent losses