1 Laboratoire Kastler Brossel (ENS, CNRS, UPMC) Institut National de MØtrologie (CNAM) Permanents S. Guellati-KhØlifa C. Schwob F. Nez L. Julien F. Biraben Ph.D Students P. CladØ M. Cadoret E. De Mirandes A new determination of the fine structure constant based on Bloch oscillations of 87 Rb atoms in a vertical optical lattice
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A new determination of the fine structure constant based ...g2pc1.bu.edu/lept06/Nez-alpha-web.pdf · 1 Laboratoire Kastler Brossel (ENS, CNRS, UPMC) Institut National de MØtrologie
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Laboratoire Kastler Brossel (ENS, CNRS, UPMC) Institut National de Métrologie (CNAM)
A new determination of the fine structure constant based on Bloch oscillations of 87 Rb atoms in a vertical optical lattice
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quantum Hall effect
137.035 990 137.036 000 137.036 010
hfs muonium
h / m(neutron)h / m(Cs)
QED
h / m
Solid statephysics
g 2 of the electron (UW)
α-1
Γp,h-90
Codata98
Codata02
h / m(Rb)
Determinations of the fine structure constant α
c4e
0
2
hπε=α
CODATA 2002 P. Mohr and B. Taylor, RMP, 77, n°1, p. 1, january 2005
RK=h/e2=µ0c/2α
ae = f (α/π)
mv=h/λg 2 of the electron (Harvard)
( )( )Xmh
)e(AXA
cR2
r
r2 ∞=α
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Two photon transition : defined momentum transfer
Low spontaneous emission
Doppler sensitive
Controllable width of the transition (pulse duration) :
F=2
F=1
5P3/2
mk2 k1
ωSHF
∆
∆ΩΩ
∝Ω 21eff
(M. Kasevich et al, Phys. Rev. Lett 66, (1991) 2297)
Recoil velocity Raman transition
a
b
νħk m
vr m2kmv
21E
mkv
222rr
r
h
h
==
=
4
Principle of our experiment
Final uncertainty : σvr = σv / (2N)
N × 2ħk
Coherent acceleration
measurement(Raman transition)
selection(Raman transition)
MOT +molasses
! selection of an initial sub-recoil velocity class! coherent acceleration : N Bloch oscillations, momentum transfer 2Nħk! measurement of the final velocity class
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Momentum
Ener
gyV
eloc
ity d
istri
butio
n
|bi
~δcenter
Ener
gy
Momentum
Determination of the center of velocity distribution