169 research outputs found
Magnetic and electric dipole moments of the state in ThO
The metastable state in the thorium monoxide (ThO)
molecule is highly sensitive to the presence of a CP-violating permanent
electric dipole moment of the electron (eEDM). The magnetic dipole moment
and the molecule-fixed electric dipole moment of this state are
measured in preparation for a search for the eEDM. The small magnetic moment
displays the predicted cancellation of
spin and orbital contributions in a paramagnetic molecular
state, providing a significant advantage for the suppression of magnetic field
noise and related systematic effects in the eEDM search. In addition, the
induced electric dipole moment is shown to be fully saturated in very modest
electric fields ( 10 V/cm). This feature is favorable for the suppression of
many other potential systematic errors in the ThO eEDM search experiment.Comment: 4 pages, 3 figure
Search for the electric dipole moment of the electron with thorium monoxide
The electric dipole moment of the electron (eEDM) is a signature of
CP-violating physics beyond the Standard Model. We describe an ongoing
experiment to measure or set improved limits to the eEDM, using a cold beam of
thorium monoxide (ThO) molecules. The metastable state in ThO
has important advantages for such an experiment. We argue that the statistical
uncertainty of an eEDM measurement could be improved by as much as 3 orders of
magnitude compared to the current experimental limit, in a first-generation
apparatus using a cold ThO beam. We describe our measurements of the state
lifetime and the production of ThO molecules in a beam, which provide crucial
data for the eEDM sensitivity estimate. ThO also has ideal properties for the
rejection of a number of known systematic errors; these properties and their
implications are described.Comment: v2: Equation (11) correcte
Enhancement of the electric dipole moment of the electron in PbO
The a(1) state of PbO can be used to measure the electric dipole moment of
the electron d_e. We discuss a semiempirical model for this state, which yields
an estimate of the effective electric field on the valence electrons in PbO.
Our final result is an upper limit on the measurable energy shift, which is
significantly larger than was anticipated earlier: .Comment: 4 pages, revtex4, no figures, submitted to PR
High-resolution saturation spectroscopy of singly-ionized iron with a pulsed uv laser
We describe the design and realization of a scheme for uv laser spectroscopy
of singly-ionized iron (Fe II) with very high resolution. A buffer-gas cooled
laser ablation source is used to provide a plasma close to room temperature
with a high density of Fe II. We combine this with a scheme for pulsed-laser
saturation spectroscopy to yield sub-Doppler resolution. In a demonstration
experiment, we have examined an Fe II transition near 260 nm, attaining a
linewidth of about 250 MHz. The method is well-suited to measuring transition
frequencies and hyperfine structure. It could also be used to measure small
isotope shifts in isotope-enriched samples.Comment: 9 pages, 5 figures, updated Fig. 3. For submission to J. Phys.
Shot-noise-limited spin measurements in a pulsed molecular beam
Heavy diatomic molecules have been identified as good candidates for use in
electron electric dipole moment (eEDM) searches. Suitable molecular species can
be produced in pulsed beams, but with a total flux and/or temporal evolution
that varies significantly from pulse to pulse. These variations can degrade the
experimental sensitivity to changes in spin precession phase of an electri-
cally polarized state, which is the observable of interest for an eEDM
measurement. We present two methods for measurement of the phase that provide
immunity to beam temporal variations, and make it possible to reach
shot-noise-limited sensitivity. Each method employs rapid projection of the
spin state onto both components of an orthonormal basis. We demonstrate both
methods using the eEDM-sensitive H state of thorium monoxide (ThO), and use one
of them to measure the magnetic moment of this state with increased accuracy
relative to previous determinations.Comment: 12 pages, 6 figure
Attaining the shot-noise-limit in the ACME measurement of the electron electric dipole moment
Experimental searches for the electron electric dipole moment, , probe
new physics beyond the Standard Model. Recently, the ACME Collaboration set a
new limit of [Nature
, 355 (2018)], constraining time reversal symmetry (T) violating
physics in the 3-100 TeV energy scale. ACME extracts from the measurement
of electron spin precession due to the thorium monoxide (ThO) molecule's
internal electric field. This recent ACME II measurement achieved an order of
magnitude increased sensitivity over ACME I by reducing both statistical and
systematic uncertainties in the measurement of the electric dipole precession
frequency. The ACME II statistical uncertainty was a factor of 1.7 above the
ideal shot-noise limit. We have since traced this excess noise to timing
imperfections. When the experimental imperfections are eliminated, we show that
shot noise limit is attained by acquiring noise-free data in the same
configuration as ACME II.Comment: 7 pages, 4 figure
Measurement of the electron electric dipole moment using YbF molecules
The most sensitive measurements of the electron electric dipole moment d_e
have previously been made using heavy atoms. Heavy polar molecules offer a
greater sensitivity to d_e because the interaction energy to be measured is
typically 10^3 times larger than in a heavy atom. We report the first
measurement of this kind, for which we have used the molecule YbF. Together,
the large interaction energy and the strong tensor polarizability of the
molecule make our experiment essentially free of the systematic errors that
currently limit d_e measurements in atoms. Our first result d_e = (- 0.2 \pm
3.2) x 10^-26 e.cm is less sensitive than the best atom measurement, but is
limited only by counting statistics and demonstrates the power of the method.Comment: 4 pages, 4 figures. v2. Minor corrections and clarifications made in
response to referee comment
Magnetic and electric dipole moments of the H^3 Δ_1 state in ThO
The metastable H^3 Δ_1 state in the thorium monoxide (ThO) molecule is highly sensitive to the presence of a CP
-violating permanent electric dipole moment of the electron (eEDM) [E. R. Meyer and J. L. Bohn, Phys. Rev. A 78, 010502 (2008)]. The magnetic dipole moment μ_H and the molecule-fixed electric dipole moment D_H of this state are measured in preparation for a search for the eEDM. The small magnetic moment μH=8.5(5)×10^(−3)μ_B displays the predicted cancellation of spin and orbital contributions in a ^3Δ_1 paramagnetic molecular state, providing a significant advantage for the suppression of magnetic field noise and related systematic effects in the eEDM search. In addition, the induced electric dipole moment is shown to be fully saturated in very modest electric fields (<10 V/cm). This feature is favorable for the suppression of many other potential systematic errors in the ThO eEDM search experiment
Controlling two-species Mott-insulator phses in an optical lattice to form an array of dipolar molecules
We consider the transfer of a two-species Bose-Einstein condensate into an
optical lattice with a density such that that a Mott-insulator state with one
atom per species per lattice site is obtained in the deep lattice regime.
Depending on collision parameters the result could be either a `mixed' or a
`separated' Mott-insulator phase. Such a `mixed' two-species insulator could
then be photo-associated into an array of dipolar molecules suitable for
quantum computation or the formation of a dipolar molecular condensate. For the
case of a Rb-K two-species BEC, however, the large inter-species
scattering length makes obtaining the desired `mixed' Mott insulator phase
difficult. To overcome this difficulty we investigate the effect of varying the
lattice frequency on the mean-field interaction and find a favorable parameter
regime under which a lattice of dipolar molecules could be generated
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