107 research outputs found
High quality anti-relaxation coating material for alkali atom vapor cells
We present an experimental investigation of alkali atom vapor cells coated
with a high quality anti-relaxation coating material based on alkenes. The
prepared cells with single compound alkene based coating showed the longest
spin relaxation times which have been measured up to now with room temperature
vapor cells. Suggestions are made that chemical binding of a cesium atom and an
alkene molecule by attack to the C=C bond plays a crucial role in such
improvement of anti-relaxation coating quality
Quantum noise limited and entanglement-assisted magnetometry
We study experimentally the fundamental limits of sensitivity of an atomic
radio-frequency magnetometer. First we apply an optimal sequence of state
preparation, evolution, and the back-action evading measurement to achieve a
nearly projection noise limited sensitivity. We furthermore experimentally
demonstrate that Einstein-Podolsky-Rosen (EPR) entanglement of atoms generated
by a measurement enhances the sensitivity to pulsed magnetic fields. We
demonstrate this quantum limited sensing in a magnetometer utilizing a truly
macroscopic ensemble of 1.5*10^12 atoms which allows us to achieve
sub-femtoTesla/sqrt(Hz) sensitivity.Comment: To appear in Physical Review Letters, April 9 issue (provisionally
Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating
The use of anti-relaxation coatings in alkali vapor cells yields substantial
performance improvements by reducing the probability of spin relaxation in wall
collisions by several orders of magnitude. Some of the most effective
anti-relaxation coating materials are alpha-olefins, which (as in the case of
more traditional paraffin coatings) must undergo a curing period after cell
manufacturing in order to achieve the desired behavior. Until now, however, it
has been unclear what physicochemical processes occur during cell curing, and
how they may affect relevant cell properties. We present the results of
nondestructive Raman-spectroscopy and magnetic-resonance investigations of the
influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene
coating the inner surface of a glass cell. It was found that during the curing
process, the alkali metal catalyzes migration of the carbon-carbon double bond,
yielding a mixture of cis- and trans-2-nonadecene.Comment: 5 pages, 6 figure
Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity
Magnetic fields generated by human and animal organs, such as the heart,
brain and nervous system carry information useful for biological and medical
purposes. These magnetic fields are most commonly detected using
cryogenically-cooled superconducting magnetometers. Here we present the frst
detection of action potentials from an animal nerve using an optical atomic
magnetometer. Using an optimal design we are able to achieve the sensitivity
dominated by the quantum shot noise of light and quantum projection noise of
atomic spins. Such sensitivity allows us to measure the nerve impulse with a
miniature room-temperature sensor which is a critical advantage for biomedical
applications. Positioning the sensor at a distance of a few millimeters from
the nerve, corresponding to the distance between the skin and nerves in
biological studies, we detect the magnetic field generated by an action
potential of a frog sciatic nerve. From the magnetic field measurements we
determine the activity of the nerve and the temporal shape of the nerve
impulse. This work opens new ways towards implementing optical magnetometers as
practical devices for medical diagnostics.Comment: Main text with figures, and methods and supplementary informatio
Rubidium "whiskers" in a vapor cell
Crystals of metallic rubidium are observed ``growing'' from paraffin coating
of buffer-gas-free glass vapor cells. The crystals have uniform square
cross-section, m on the side, and reach several mm in length.Comment: 2 pages, 1 figur
Relaxation of atomic polarization in paraffin-coated cesium vapor cells
The relaxation of atomic polarization in buffer-gas-free, paraffin-coated
cesium vapor cells is studied using a variation on Franzen's technique of
``relaxation in the dark'' [Franzen, Phys. Rev. {\bf 115}, 850 (1959)]. In the
present experiment, narrow-band, circularly polarized pump light, resonant with
the Cs D2 transition, orients atoms along a longitudinal magnetic field, and
time-dependent optical rotation of linearly polarized probe light is measured
to determine the relaxation rates of the atomic orientation of a particular
hyperfine level. The change in relaxation rates during light-induced atomic
desorption (LIAD) is studied. No significant change in the spin relaxation rate
during LIAD is found beyond that expected from the faster rate of spin-exchange
collisions due to the increase in Cs density.Comment: 14 pages, 14 figure
Electric-field-induced change of alkali-metal vapor density in paraffin-coated cells
Alkali vapor cells with antirelaxation coating (especially paraffin-coated
cells) have been a central tool in optical pumping and atomic spectroscopy
experiments for 50 years. We have discovered a dramatic change of the alkali
vapor density in a paraffin-coated cell upon application of an electric field
to the cell. A systematic experimental characterization of the phenomenon is
carried out for electric fields ranging in strength from 0-8 kV/cm for
paraffin-coated cells containing rubidium and cells containing cesium. The
typical response of the vapor density to a rapid (duration < 100 ms) change in
electric field of sufficient magnitude includes (a) a rapid (duration of < 100
ms) and significant increase in alkali vapor density followed by (b) a less
rapid (duration of ~ 1 s) and significant decrease in vapor density (below the
equilibrium vapor density), and then (c) a slow (duration of ~ 100 s) recovery
of the vapor density to its equilibrium value. Measurements conducted after the
alkali vapor density has returned to its equilibrium value indicate minimal
change (at the level of < 10%) in the relaxation rate of atomic polarization.
Experiments suggest that the phenomenon is related to an electric-field-induced
modification of the paraffin coating.Comment: 15 pages, 15 figure
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