Download - JLee PhD Defense Presentation 2012
-
1 m
Optical Spectroscopy of Tungsten Carbide
for electron EDM Measurement
Jeongwon Lee Leanhardt AMO group
Department of Physics, University of Michigan
Portrait of Edward James Rene Magritte (1937)
P-violation
S ed+
_
Electron with
Non-zero EDM
-
1. Introduction
- what is an electron Electric Dipole Moment (eEDM)?
- eEDM measurement scheme
- advantages of WC molecules
2. Experimental Results
- 1st generation : continuous supersonic beam source
- 2nd generation : pulsed supersonic beam source
3. Uncertainty Analysis
- Systematic uncertainty
- Statistical uncertainty
4. Summary
Contents
-
1. Introduction
Contents
-
electron EDM violates symmetry
Non-zero electron Electric Dipole Moment
Violates both time (T) and parity (P) reversal symmetry
-
e- EDM : not detected yet d
e [e
*cm
]
10-38
10-28
10-30
10-32
10-34
10-36
10-40
SU
SY
Mu
lti-H
igg
s
Le
ft-R
igh
t
10-24
10-26
Current Experimental Limit :
|de| < 1.05 x 10-27 e*cm [~10-18 Debye]
Improving the precision of e-EDM measurement
=> Probe for new physics beyond Standard Model
Standard Model
Too far from current experimental limit
-
S ed1m
1m
deE
S ed
BB
BB
deE
E B
+
_ +
_
EDM Measurement Scheme
- Case 1 : E & B Field Parallel
Total Shift 1:
0m
h
EdB emtotal
221,
-
S ed1m
1m
deE
S ed
BB
BB
deE
E B
+
_ +
_
EDM Measurement Scheme
- Case 2 : E & B Field anti-Parallel
0m
Reversing E field relative to B field
=> Stark Shift in opposite direction Total Shift 2:
h
EdB emtotal
222,
E
vvd
totaltotal
e4
2,1,
-
Elab
[1] B.C. Regan, E.D. Commins, C.J. Schmidt & D. DeMille [PRL 88, 071805 (2002)]
[2] J.J. Hudson, D.M. Kara, I.J. Smallman, B.E. Sauer, M. R. Tarbutt & E.A. Hinds [Nature 473, 493-496 (2011)]
Effective Electric Field : E-field seen by e- inside
atoms and molecules
- Maximum Elab ~ 105 V/cm
- High Z atoms : Eeff ~ 107 V/cm
Upper Limit from Tl expt.[1] : |de| < 1.6 x 10-27 e*cm [~10-18 Debye]
- Heavy Polar Molecules : Eeff ~ 1010 V/cm
Upper Limit from YbF expt.[2] : |de| < 1.05 x 10-27 e*cm
Advantage 1: Large Electric Field
- Heavy Polar Molecule
-
When g ~ 2 and g ~ 1, g ~ 0
Very Small magnetic moment:
measured to be g = 0.022 [1]
1
3
1
2
1
spin:
orbital:
spin + orbital:
+ = Spin & orbital projection
in opposite direction
Advantage 2: Small Magnetic Moment
- 3 1 state of WC
[1] F. Wang & T.C. Stemlie, JCP 135 104313 (2011)
-
Elab
Advantage 3: Internal Comagnetometer
- -doublet structure of WC
0effE
0effE
1m 0m 1m
elElab elElab
elElab elElab
Small doublet splitting (nearly degenerate opposite parity states)
=> Efficient Zeeman Shift Cancellation
B
-
2. Experimental Results
Contents
-
LIF Spectroscopy
3 transitions per J level.
WC Molecular Spectrum
Ro-vibrational ground state => EDM state
X 3 1
[20.6] =2
R(1) line
R transition : J = +1
Q transition : J = 0
P transition : J = - 1
e = 983.2 cm-1
~ 1400 K
B = 0.509 cm-1 ~ 0.7 K
-
Rotational Temperature Requirement
Fractional ro-vibrational
ground state @ 1000 K ~ .001
@ 100 K ~ .01
We want colder molecules!
Most general way of Cooling to
1K level : supersonic expansion
(Fractional EDM state)
B = 0.509 cm-1 ~ 0.7 K
e = 983.2 cm-1 ~ 1400 K
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1st generation experiment:
Continuous WC molecular beam apparatus
1. Evaporation
Zone
(Seeding Zone)
3. Optical
Spectroscopy
Zone
2. Differential
Pumping Zone
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1. Evaporation Zone
- Seeding Technique
Resistive Heating Method
24 2HWCCHW
W WC 182W
183W
184W 186W
1% molecular formation
Tungsten Vapor Pressure
=> 1 X 10-6 Torr at 2700K
Compare with,
Ytterbium Vapor Pressure
=> 7 Torr at 1000K
-
1. Evaporation Zone
- Cooling Mechanism
Tungsten Filament (~150W)
(Resistive Heating Method)
1. Far from the throat of the nozzle, Thermalization process dominates
=> Energy Transfer from W / WC to Buffer gas molecule
2. Closer to the throat, Supersonic Effect dominates
=> Converting thermal energy into direct kinetic motion
Thermalization E. Conversion
Supersonic Effect
-
Continuous WC molecular beam apparatus 2. Differential Pumping Zone
- Pumping Capacity Issue
Too Much Flux is Lost!
-
Continuous WC molecular beam apparatus 2. Differential Pumping Zone
- How to overcome the pumping capacity
2cm
25 cm
Flux regained by
decreasing the
nozzle-skimmer distance
-
3. Optical Spectroscopy Zone
Tungsten Supersonic Beam Characterization
Top View
Side View of
Spectroscopy
Chamber
Calculated
Photon
Collection
efficiency
= 0.063
Radial Probe
@ 384.9nm
Axial Probe
@ 384.9nm
Laser Induced Fluorescence
Spectroscopy of Tungsten 5D0 5F1
384.9nm
5D0 (Ground State)
5F1
Atomic /
Molecular Beam
-
Flux Separation Technique
- Atom Flux / Radiated Light Flux
Flux passing through nozzle & skimmer (2 apertures)
Filament light background reduced by a factor of 1000,
while the LIF signal decreased only by a factor of 5
Signal to Noise
Increase by factor of 6
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Continuous WC molecular beam apparatus Tungsten LIF spectrum
- 1 Torr Argon, 1.5mm Nozzle, 3mm Skimmer
1.8 GHz
(vaxial~681m/s)
260 MHz
(~40K) 90 MHz
(~0.05 rad)
10/67
/681
2
5 sm
sm
m
Tk
v
a
vM
tungsten
transB
axialaxial at supersonic regime
-
LIF signal of WC molecules was not detected from the continuous beam.
=> 2nd generation pulsed supersonic beam source was developed.
Tungsten
Signal to Noise
~1200
Tungsten Carbide
Ground State
(estimated) Signal to Noise
Tungsten Carbide
Molecular Formation
~1% X X
Tungsten Carbide
In Rovibrational
Ground State
at 40K,
~5% ~0.6
-
Advantage of pulsed beam
- Diagram of Ideal Case
Atomic
Flux
(Signal)
Photon
Counter
gate
Radiated
Light Flux
(Noise)
Time Delay (= time of flight)
-
Pulse Valve
485nm diode laser
Tungsten Rod
Nd:YAG Laser
PMT
Vacuum Pump
350psi
90% Argon
+ 10% CH4
W + CH4 WC + 2H2
Detect Laser Induced Fluorescence of WC,
75 cm away from the source
2nd generation experiment:
Pulse WC molecular beam apparatus
-
LIF Spectroscopy
First detected signal !
WC Molecular Spectrum
Ro-vibrational ground state => EDM state
1110 sN
~10MHz
X 3 1
[20.6] =2
R(1) line
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3. Uncertainty Analysis
Contents
-
Elab~10V/cm
X3 1 ground state of WC molecules
0effE
0effE
1m 0m 1m
elElab elElab
elElab elElab
Advantages of X3 1 State WC Molecules for eEDM experiments
B
Large Effective Electric Field Zeeman Shift Cancellation with doublet
calculated
Eeff~-36GV/cm
[1] A.N. Petrov & A.V. Titov, private communication
[1]
Other eEDM experiments with 3 1 State Molecules: JILA (HfF+ , ThF + ), Harvard/Yale (ThO)
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Elab~10V/cm
Uncertainties of the Measurement Scheme
0effE
0effE
1m 0m 1m
elElab elElab
elElab elElab
Uncertainties of the eEDM measurement scheme with WC
B
Large Effective Electric Field
=> how accurate is the calculation?
Zeeman Shift Cancellation with doublet
How close are the g factors?
(ge and gf)
calculated
Eeff~-36GV/cm ge
gf
-
WC|
Uncertainty in
Uncertainty in
Hyperfine constant
measurement
Uncertainty in
Eeff field
2/12/1|
| where
2
2
02
0
psrelreleffr
ra
a
ZeE
[1]
[1] I.B. Khriplovich & S.K. Lamoreaux, CP violation without Strangeness (1997)
Uncertainty Analysis 1
- Effective electric field
WCWCr
|1
|2 WChyperfineWC
H ||
Near the heavy nucleus, electric field seen by the electron ( ) can be written as, effE
-
Tungsten Carbide R lines
LIF spectroscopy of R branches of [20.6] =2 Lower J lines have larger splittings
-
Hyperfine Structure of 183W12C
( I = )
183W12C
R(1)
183W12C
R(2)
a b
c
c a
)1(2
)1()1()1(
JJ
IIJJFFhSplittingHyperfine
(excited) 131258
(ground) 121171
2
1
MHzh
MHzh
-
[1] F. Wang & T.C. Stemlie, JCP 134 201106 (2011)
[2] A.N. Petrov & A.V. Titov, private communication
Uncertainty Analysis 1
- Effective electric field
Hyperfine measurement as the test of electronic wavefunction near the nucleus
MHz 121171
Our expt. Previous expt. Calculated
MHz 6011MHz 511363
[2] [1]
WC|
Uncertainty in
Uncertainty in
Hyperfine constant
measurement
Uncertainty in
Eeff field
WCWCr
|1
|2 WChyperfineWC
H ||
-
0effE
0effE
1m 0m 1m
elElab elElab
elElab elElab
There is a small difference in g factors ( between top and bottom doublet.
effeefBef EdggB 4)(2
gBSystematic B2ty Uncertain
Uncertainty Analysis 2
- Difference in g factors
-
Summary of relation between
-doublet and
Smaller -doublet Smaller Elab to
fully polarized WC Smaller
g
)g(
rotation
labelab
B
EE
labedoublet EH
Polarization condition
-
Change in Experimental Settings
)1(~ JJoHdoublet)1(2
)1()1()1(
JJ
IIJJFFhHHyperfine
Low Trot Preferred High Trot Preferred Under-expansion & Higher YAG power
-
Change in Experimental Settings
- Axial Velocity Distribution
)1(~ JJoHdoublet)1(2
)1()1()1(
JJ
IIJJFFhHHyperfine
Low Trot Preferred High Trot Preferred
Under-expansion &
Higher YAG power
-
Doublet
- Experimental Data
)2)(1()1(~2)1(~2
21 JJJJoJJo
SplittingDoublet
e/f
f/e
f/e
e/f
For R
branch )2)(1()1(~2 2 JJJJo
)1(~2 1 JJo
kHzo
kHz
kHzo
1.1~)13400 : (previous
18418~
2
1
182W12C
184W12C
186W12C
R(4) R(5)
Based on fitting,
[1]
[1] F. Wang & T.C. Stemlie, JCP 136 044316 (2012)
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Systematic Uncertainty from
Smaller -doublet Smaller Elab to
fully polarized WC Smaller
-5103g(10V/cm)kHzo 18418~1
Smaller
systematic
uncertainty
10V/cmlabE
)/36~E(when level 10dat y sensitivit thelimits
G)~B(when 1002ty Uncertain
eff
29-
e cmGVcme
HzgBSystematic B
-
* J. Lee, J. Chen, L. Skripnikov, A. Petrov, A. Titov, A. Leanhardt, full manuscript in preparation
Further Suppression of
Systematic Uncertainty from
Detailed calculation revealed a g-factor crossing point => suppression of systematics as
-
* J. Lee, J. Chen, L. Skripnikov, A. Petrov, A. Titov, A. Leanhardt, full manuscript in preparation
Further Suppression of
Systematic Uncertainty from
g-factor crossing point results at Elab = 2V/cm
Need to check whether the molecule is fully polarized
=> Eeff = 0.85 * 36GV/cm when Elab = 2V/cm
-
++++++++++++++++
- - - - - - - - - - - - - - -
sin2( )
cos2( )
E E B B
/2 /2
L ~ 1 m, v ~ 300 m/s, ~ 3 ms populations
oscillate
Chop relative direction of E and B and measure frequency difference.
ei
TN2
1
Frequency Resolution :
Statistical Uncertainty of
Ramsey Spectroscopy
-
Statistical Uncertainty of
eEDM measurement
TN2
1
Frequency Resolution :
Rate of EDM state
measurement
Increase of
molecular density
Stronger transition
Coherence time
(= time of flight)
Beam line extension
Integration time
Taking more
measurements
at a fixed rate
-
Statistical Uncertainty of
eEDM measurement
From beam line extension
h
Ed effe2
TN2
1EDM Shift :
Frequency
Resolution :
VS.
Current Status Future Plan
Eeff -36GV/cm -36GV/cm
~1ms ~2ms
~10 Hz ~104 Hz
T 1day (~105s) 1day (~105s)
|de| detection limit < 10-27 e-cm < 10-29 e-cm
N From probing 545nm transition with higher
Frank-Condon factor*
* M. Morse, private communication
-
* Dispersed Fluorescence data, courtesy of M. Morse group
Improvement in Frank Condon Factor
FC factors
calculated from
RKR method
(R. Le Roy group)
-
Conclusion & Summary
Motivation
Search of Time symmetry violation
Measurements
Hyperfine Sys. Uncertainty
of Eeff field
Doublet Sys. Uncertainty
of g
WC Beam Stat. Uncertainty
Methods
3 1 ground state of WC molecules
Conclusion
Identified 3 1 state of WC as candidate system for eEDM expt.
Analyzed systematic & statistical
uncertainties for eEDM expt.
with projected sensitivity of
|de| < 10-27 e-cm
-
Thank You
Top Row: Jinhai Chen, Aaron Leanhardt, Emily Alden
Bottom Row: Kaitlin Moore, Yisa Rumala, Chris Lee, Erika Etnyre