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Experimental Atomic Physics Research in the Budker Group
• Tests of fundamental symmetries using atomic physics:• Parity
• Time-reversal invariance
• Permutation Postulate/Spin-Statistics Connection
• Temporal variation of fundamental “constants”
• Applied atomic spectroscopy• Sensitive magnetometry and electrometry
• Nonlinear optics with atoms
• Optical properties of superfluid helium
• “New” atomic energy levels
• Properties of complex atoms: the rare earths, Ba
Group Demographics and Philosophy
• 6 graduate students
• 1 - 3 undergrads
• 2 staff scientists (1 senior, 1 junior)
• Part-time technician
• Lots of visitors from US and abroad
• Each student has their own project
• Lots of interactions within group
• Variety of experiences and techniques: lasers, optics, atomic beams and vapor cells, cryogenics, computer control and data acquisition, vacuum, electronics, theory, scientific writing and editing, …..
Further information:
• http://socrates.berkeley.edu/~budker
• Office: 273 Birge; labs: 217,219,221,230,241, and 245 Birge
Z
e
e
Weak interaction
(violates parity)) r ( = ) r (
Electromagnetic
interaction
(conserves parity)) r ( ) r (
Atomic Parity Nonconservation
Small Modifications of the Optical Properties of Atoms
Provides Unique Low-Energy Test of the Standard Model
CollimatorYtterbium atoms
Oven
PBC mirror
Parabolic reflector
Lightguide
BE
zx
y
Photo-multiplier tubes
Electric field plates
Magnetic field coils
408-nm light
649-nm lighte
Electric and magnetic fields define a handedness
PNC effects show up as dependence of atom-photon interaction on handedness
PNC Experiments
Two Experiments in Progress: Dysprosium (Z=66) and Ytterbium (Z=70)
How constant is the fine structure “constant” ?
Theories that unify gravity with other forces either
allow or necessitate variation
THEORETICAL
Laboratory:•H-maser vs. Hg+ microwave clock:
/< 3.7 10-14 /yr
•Rb vs. Cs microwave clocks:/< 1.1 10-14 /yr
•Hg+ optical vs. Cs microwave clocks:
/< 1.2 10-15 /yr
.
.
.
Geophysical:Oklo natural nuclear reactor
1.8 billion years ago: /< 10-18 /yr
.
Astrophysical:
[J. K. Webb, et al. , Phys. Rev. Lett. 87, 091301 (2001).]
/= (-7.2 1.8) 10-16 /yr
.
EXPERIMENTAL
A B
Ground State0
20,000
En
erg
y (c
m-1)
levels A and B are highly sensitive to
variations in
in dysprosium
’
~ 3-2000 MHz
atomic beam
PMT
atomic freq. standard
rf freq. generator
fluor.
E-field plates
~ 21015 Hz |/|
i.e. for |/| ~ 10-15 /yr
~ 2 Hz/yr
NONLINEAR MAGNETO-OPTICAL NONLINEAR MAGNETO-OPTICAL ROTATIONROTATION
Goal: Obtain highest possible sensitivity to magnetic fields.
Use laser light to polarize atoms:(1) Aligns magnetic dipole moments;(2) Creates preferred optical axis.
F = 1
F’ = 0
MF = -1 MF = 0 MF = +1
Magnetic moments precess in magnetic field:Optical axis rotates causes light polarization to rotate.
gFrel
gFrel)2
-1.0 -0.8 -0.6 -0.4 -0.2 -0.0 0.2 0.4 0.6 0.8 1.0
Magnetic Field (nT)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Rot
atio
n A
ngl
e (m
rad)
Paraffin-coated cells smuggledin as Christmas ornaments!
rel1 Hz
Slow relaxation of atomic polarization:
~ 1 G ~ 0.1 nT
(For FSB agents: this is a joke!)
Precision magetometry and atomic EDM measurement using spin-polarized atoms in
a buffer gas at cryogenic temperatures
• Problem: to measure very small B; to measure electron EDM
• Paramagnetic atom magnetometer; He buffer gas at T=4K to increase spin-relaxation time to minutes
Measuring the Kerr effect in LHe and the LANL neutron EDM experiment
• Problem: to measure strong electric fields (50kV/cm) inside a bath of LHe at 300mK.
• Kerr effect: an initially isotropic medium acquires birefringence when electric field is applied, measure this.
Light Guides Cells BetweenElectrodes
HV and Ground Electrodes
Beam Entrance Window
HV Variable Capacitor
SQUID Enclosure
Cos Coil
Neutron EDM experiment at LANSCE
Motivation: BEV exp
Lifetimes, branching ratios, new levels, polarizabilities (Ba)
Unusually large polarizabilities
“new” opposite-parity levelsElectron EDM expNoncontact circuit board testing
(100 times; for n<10, only smaller than 2s,2p of H)
Laser spectroscopy for Laser spectroscopy for fundamental symmetry testsfundamental symmetry tests
6s6p 1P1
6s6p 3P0,1,2
Laser Excitation 554.7 nm
Fluorescence~ 435 nm
6s2 1S0
Probed States
Even Parity Odd Parity
559 - 569.5 nm
Laser Excitation