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Investigation of the Use of He-Diatomic Van der Waals Complexes as a Probe of Time Reversal Violation
Jacob Stinnett, Dr. Neil Shafer-Ray, and Dr. Eric AbrahamHomer L. Dodge Department of Physics
University of Oklahoma
This work was funded by the National Science Foundation (NSF-0855431.)
66th OSU International Symposium on Molecular SpectroscopyJune 24, 2011
Outline
• Motivation
• A remarkable observation of pure Stark spectroscopy in NO
• Simple vector model of a extremely weak
He-NO van der Waals complex
• Suspicions
• Implications for an e-EDM measurement
Fabry-Pérot Type Resonator: Spherical Reflectors
PbF
Fourier Transform Microwave Spectrometer: Pure rotational absorption spectrom of the X1 state of PbF. (Collaborators Jens-Uwe Grabow, Richard Mawhorter Hanover Germany)
0 2 4 6 8 1 0
1 2
1 0
8
6
4
2
0
Ek V c m
mH
z10^27
ecm
eEDM of the J12 F1 ,M 1 s tate o f P bF
Many e-EDM candidates require a large (~10kV/cm) field to becomesensitive.
Similar curves forBaF, HgF, YbF
This study was motivated a series of remarkable experimentsinvolving pure Stark spectroscopy of the NO molecule.
Chem Phys Let 341 2001 495.
A DC electric field of order 14 v/cm is crossed with an RF electric field of similar amplitude.At resonant frequencies, the population of NO, as viewed at non-state selective detector, isobserved.
Non state-selective 266nm ionization
The Truly Incredible Amazing
Result
Caceres et al measured a completely linear Stark effect in NO with simple transitions given by
for JU=1/2, 3/2, and 5/2
D = 0.15782(2) Debye Ap J 161 (1970) 779
BUT . . .
D= 0.1578(4) Debye CPL 426 (2006)214
Chem Phys Let 426 2006 214
Two 2P1/2 electronic states form the ground state
Z
YX
W- [Rxz -, Ryz +]W+ [Rxz +, Ryz -]
Y
Z
X
21
21 |1| W = | L + S |=1/2 gives projection of
angular momentum on the nuclear axis: orbital a.m.
(=1 for P states)spin a.m.
(±1/2 because this is a 2P state.)
Motion of the Nuclei
Although the electrons are light, their net angular momentum isnot much smaller than that of the nuclei.
Nuclei move as a symmetric top.
Com
bine
to fo
rm W
+
wav
e fu
nctio
n
Com
bine
to fo
rm W
-
wav
e fu
nctio
n
PARI
TY
PARI
TYIn the absence of an applied field, the wave functions are eigenvectors of parity
and hence have no net dipole moment.
Combined electronic and nuclear motion, DE<<DUW
up
down
For a strong electric field, the wave functions are either pointed up or down and one expects a linear Stark effect.
Combined electronic and nuclear motion DE>>DUW
MotivationThe Stark effect in NO is described by
D is the dipole moment of NOE is the electric field
Parity splitting~= 10 GHz for 2Π1/2 NO~= 10 MHz for 2Π3/2 NO
2222
2
1
21
Jp
JJ
mEDU Stark
Motivation
What suppressed the parity splitting?!!#!@!.
+MAGIC
2222
2
1
21
Jp
JJ
mEDU Stark
“At present we have no explanation why the best fit is obtained with the resonant transition calculated with eq 2.”
In this work we investigate the possibility that a novel He-NO van der Waals complex is responsible for this behavior.
N
Possible He-NO Rydberg-Like van der Waals Complex
O
He
extE�������������� (1) He must be far enough away
so thatDHe <<DNO.
(2) He must be close enoughso that the He-NO van der Waalsinteraction is stronger than the
parity splitting.
Possible for He-NO(2P3/2) at ~ 20 Angstroms.
extNO
extHeNO
EDU
EDDU
)(
)(
Because the van der Waals energy must be much less thanthe rotational energy, the interaction may be treated as a perturbation
to the NO spin rotational Hamiltonian
SR vdw StarkH H H H
222
3
221 1
2 0 12 23
ˆ ˆ3 12
4 4
2ˆ ˆ ˆ ˆ ˆ ˆ( ) ( ) ( )
4
vdwo
dcm cm cmR
o
n sDH
R
DP n r P n r P n r
R
For the case of dipole-flipping transitions with
|MHe|=JHe= |M| = ½, W=3/2, this reduces to
This theory leads to a linear Stark effect that follows a simple vector model at low fields.
(Ignoring E Dinduced)
A Simple Vector Model
This simple model allows us to recover their formula.
3
Our model explains lines that Caceras et al have assigned to a J=3/2, J=5/2 transition.
It also does a reasonable job predicted the substructure surrounding these lines.
For the JU = 1/2 line, this vector model can not explain the observation.
2/5'
2/1||
2/3
HeHeHe mmJ
m
J
2/1'
2/1||
2/3
HeHeHe mmJ
m
J
ExperimentalTheoretical
• The He-NO bond distance required to suppress the parity splitting leads to a polarized He atom that changes the magnitude of the Stark interaction by much more than 0.2%.
Suspicions
Chem Phys Let 426 2006 214
1) A simple model indicates that the polarizability of a He-NO complex may be much greater than that of NO and gives reasonable agreement to the J=3/2 and J=5/2 lines observed by Caceres et al.
2) We cannot explain the magnitude of the linear Stark effect observed by Caceres et al and suspect their data analysis may be flawed. It is likely that their data is probing a known rather than exotic He-NO species.
3) He-[eEDM molecule] clusters formed in laser ablation sources may have increased polarizability and hence be worth investigating.
Conclusions
Acknowledgements
Dr. Neil Shafer Ray
Dr. Eric Abraham
NSF
Questions?
NO(2P3/2)-He(slow moving) + hnRF NO(2P3/2)-He(fast moving)
NO(2P3/2)-He(fast moving) + NO NO(2P1/2) + He + NO + kinetic energy
Resonant thermalization of the Omega-Doublet energy (120 cm-1/molecule) and transverse kinetic energy of the beam (~1E-3 cm-1/ molecule).
Zeeman-effect in PbF(X1) pure rotational spectra
B = 0
DM = 0 DM = +/-1
~3 kHz
FREQUENCY / MHz22574.4 22575.4