117 research outputs found
Magnetic shielding and exotic spin-dependent interactions
Experiments searching for exotic spin-dependent interactions typically employ
magnetic shielding between the source of the exotic field and the interrogated
spins. We explore the question of what effect magnetic shielding has on
detectable signals induced by exotic fields. Our general conclusion is that for
common experimental geometries and conditions, magnetic shields should not
significantly reduce sensitivity to exotic spin-dependent interactions,
especially when the technique of comagnetometry is used. However, exotic fields
that couple to electron spin can induce magnetic fields in the interior of
shields made of a soft ferro- or ferrimagnetic material. This induced magnetic
field must be taken into account in the interpretation of experiments searching
for new spin-dependent interactions and raises the possibility of using a flux
concentrator inside magnetic shields to amplify exotic spin-dependent signals.Comment: 8 pages, 5 figure
How do you know if you ran through a wall?
Stable topological defects of light (pseudo)scalar fields can contribute to
the Universe's dark energy and dark matter. Currently the combination of
gravitational and cosmological constraints provides the best limits on such a
possibility. We take an example of domain walls generated by an axion-like
field with a coupling to the spins of standard-model particles, and show that
if the galactic environment contains a network of such walls, terrestrial
experiments aimed at detection of wall-crossing events are realistic. In
particular, a geographically separated but time-synchronized network of
sensitive atomic magnetometers can detect a wall crossing and probe a range of
model parameters currently unconstrained by astrophysical observations and
gravitational experiments.Comment: 5 pages, 2 figure; to appear in the PR
Influence of magnetic-field inhomogeneity on nonlinear magneto-optical resonances
In this work, a sensitivity of the rate of relaxation of ground-state atomic
coherences to magnetic-field inhomogeneities is studied. Such coherences give
rise to many interesting phenomena in light-atom interactions, and their
lifetimes are a limiting factor for achieving better sensitivity, resolution or
contrast in many applications. For atoms contained in a vapor cell, some of the
coherence-relaxation mechanisms are related to magnetic-field inhomogeneities.
We present a simple model describing relaxation due to such inhomogeneities in
a buffer-gas-free anti-relaxation coated cell. A relation is given between
relaxation rate and magnetic-field inhomogeneities including the dependence on
cell size and atomic spices. Experimental results, which confirm predictions of
the model, are presented. Different regimes, in which the relaxation rate is
equally sensitive to the gradients in any direction and in which it is
insensitive to gradients transverse to the bias magnetic field, are predicted
and demonstrated experimentally.Comment: 6 pages, 4 figures, Submitted to Phys. Rev.
Nonlinear magneto-optical rotation with modulated light in tilted magnetic fields
Larmor precession of laser-polarized atoms contained in
anti-relaxation-coated cells, detected via nonlinear magneto-optical rotation
(NMOR) is a promising technique for a new generation of ultra-sensitive atomic
magnetometers. For magnetic fields directed along the light propagation
direction, resonances in NMOR appear when linearly polarized light is
frequency- or amplitude-modulated at twice the Larmor frequency. Because the
frequency of these resonances depends on the magnitude but not the direction of
the field, they are useful for scalar magnetometry. New NMOR resonances at the
Larmor frequency appear when the magnetic field is tilted away from the light
propagation direction in the plane defined by the light propagation and
polarization vectors. These new resonances, studied both experimentally and
with a density matrix calculation in the present work, offer a convenient
method for NMOR-based vector magnetometry.Comment: Submitted to Phys. Rev. A, 6 pages, 9 figure
Constraints on short-range spin-dependent interactions from scalar spin-spin coupling in deuterated molecular hydrogen
A comparison between existing measurements and calculations of the scalar
spin-spin interaction (J-coupling) in deuterated molecular hydrogen (HD) yields
stringent constraints on anomalous spin-dependent potentials between nucleons
at the atomic scale (). The dimensionless coupling constant
associated with exchange of pseudoscalar (axion-like)
bosons between nucleons is constrained to be less than for
boson masses in the range of . This represents improvement by a
factor of about 100 over constraints placed by measurements of the
dipole-dipole interaction in molecular . The dimensionless coupling
constant associated with exchange of a heretofore
undiscovered axial-vector boson between nucleons is constrained to be
for bosons of mass , improving constraints at this distance scale by a factor of 100 for
proton-proton couplings and more than 8 orders of magnitude for neutron-proton
couplings. This limit is also a factor of 100 more stringent than recent
constraints obtained for axial-vector couplings between electrons and nucleons
obtained from comparison of measurements and calculations of hyperfine
structure.Comment: 4 pages 2 figure
Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry
We report the use of an atomic magnetometer based on nonlinear
magneto-optical rotation with frequency modulated light (FM NMOR) to detect
nuclear magnetization of xenon gas. The magnetization of a
spin-exchange-polarized xenon sample (cm at a pressure of bar,
natural isotopic abundance, polarization 1%), prepared remotely to the
detection apparatus, is measured with an atomic sensor (which is insensitive to
the leading field of 0.45 G applied to the sample; an independent bias field at
the sensor is G). An average magnetic field of nG induced by
the xenon sample on the 10-cm diameter atomic sensor is detected with
signal-to-noise ratio , limited by residual noise in the magnetic
environment. The possibility of using modern atomic magnetometers as detectors
of nuclear magnetic resonance and in magnetic resonance imaging is discussed.
Atomic magnetometers appear to be ideally suited for emerging low-field and
remote-detection magnetic resonance applications.Comment: 4 pages, 4 figure
Production and detection of atomic hexadecapole at Earth's magnetic field
Anisotropy of atomic states is characterized by population differences and
coherences between Zeeman sublevels. It can be efficiently created and probed
via resonant interactions with light, the technique which is at the heart of
modern atomic clocks and magnetometers. Recently, nonlinear magneto-optical
techniques have been developed for selective production and detection of higher
polarization moments, hexadecapole and hexacontatetrapole, in the ground states
of the alkali atoms. Extension of these techniques into the range of
geomagnetic fields is important for practical applications. This is because
hexadecapole polarization corresponding to the Zeeman coherence,
with maximum possible for electronic angular momentum and
nuclear spin , is insensitive to the nonlinear Zeeman effect (NLZ). This
is of particular interest because NLZ normally leads to resonance splitting and
systematic errors in atomic magnetometers. However, optical signals due to the
hexadecapole moment decline sharply as a function of magnetic field. We report
a novel method that allows selective creation of a macroscopic long-lived
ground-state hexadecapole polarization. The immunity of the hexadecapole signal
to NLZ is demonstrated with F=2 Rb atoms at Earth's field.Comment: 4 pages, 5 figure
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