261 research outputs found
Building one molecule from a reservoir of two atoms
Chemical reactions typically proceed via stochastic encounters between
reactants. Going beyond this paradigm, we combine exactly two atoms into a
single, controlled reaction. The experimental apparatus traps two individual
laser-cooled atoms (one sodium and one cesium) in separate optical tweezers and
then merges them into one optical dipole trap. Subsequently, photoassociation
forms an excited-state NaCs molecule. The discovery of previously unseen
resonances near the molecular dissociation threshold and measurement of
collision rates are enabled by the tightly trapped ultracold sample of atoms.
As laser-cooling and trapping capabilities are extended to more elements, the
technique will enable the study of more diverse, and eventually more complex,
molecules in an isolated environment, as well as synthesis of designer
molecules for qubits
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
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
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
Nonlinear Stress Fluctuation Dynamics of Sheared Disordered Wet Foam
Sheared wet foam, which stores elastic energy in bubble deformations, relaxes
stress through bubble rearrangements. The intermittency of bubble
rearrangements in foam leads to effectively stochastic drops in stress that are
followed by periods of elastic increase. We investigate global characteristics
of highly disordered foams over three decades of strain rate and almost two
decades of system size. We characterize the behavior using a range of measures:
average stress, distribution of stress drops, rate of stress drops, and a
normalized fluctuation intensity. There is essentially no dependence on system
size. As a function of strain rate, there is a change in behavior around shear
rates of .Comment: accepted to Physical Review
Fundamental Physics in Small Experiments
High energy physics aims to understand the fundamental laws of particles and
their interactions at both the largest and smallest scales of the universe.
This typically means probing very high energies or large distances or using
high-intensity beams, which often requires large-scale experiments. A
complementary approach is offered through high-precision measurements in small-
and mid-scale size experiments, often at lower energies. The field of such
high-precision experiments has seen tremendous progress and importance for
particle physics for at least two reasons. First, they exploit synergies to
adjacent areas of particle physics and benefit by many recent advances in
experimental techniques. Together with intensified phenomenological
explorations, these advances led to the realization that challenges associated
with weak couplings or the expected suppression factors from the mass scale of
new physics can be overcome with such methods. Second, many of these
measurements add a new set of particle physics phenomena and observables that
can be reached compared to the more conventional methodologies using high
energies. Combining high-precision, smaller-scale measurements with the
large-scale efforts therefore casts a wider and tighter net for possible
effects originating from physics beyond the Standard Model.
This report presents a broad set of small-scale research projects that could
provide key new precision measurements in the areas of electric dipole moments,
magnetic dipole moments, fermion flavor violation, tests of spacetime
symmetries, and tests with gravity. The growing impact of these high-precision
studies in high energy physics and the complementary input they provide
compared to large-scale efforts warrants strong support over the next decades.
In particular, EDM searches are expected to improve sensitivities by four or
more orders of magnitude in the next decade or two.Comment: Snowmass 2021 Community Study on the Future of Particle Physics, Rare
Processes and Precision Measurements Frontier, Topical Group RF3 Report v2: 3
additional references and one co-author adde
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
Building one molecule from a reservoir of two atoms
Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combine exactly two atoms into a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms (one sodium and one cesium) in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photo-association forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits
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