50 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
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
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
Detection of low-conductivity objects using eddy current measurements with an optical magnetometer
Detection and imaging of an electrically conductive object at a distance can
be achieved by inducing eddy currents in it and measuring the associated
magnetic field. We have detected low-conductivity objects with an optical
magnetometer based on room-temperature cesium atomic vapor and a
noise-canceling differential technique which increased the signal-to-noise
ratio (SNR) by more than three orders of magnitude. We detected small
containers with a few mL of salt-water with conductivity ranging from 4-24 S/m
with a good SNR. This demonstrates that our optical magnetometer should be
capable of detecting objects with conductivity 1 and opens
up new avenues for using optical magnetometers to image low-conductivity
biological tissue including the human heart which would enable non-invasive
diagnostics of heart diseases.Comment: Main article with supplemental materia
Controlling atomic vapor density in paraffin-coated cells using light-induced atomic desorption
Atomic-vapor density change due to light induced atomic desorption (LIAD) is
studied in paraffin-coated rubidium, cesium, sodium and potassium cells. In the
present experiment, low-intensity probe light is used to obtain an absorption
spectrum and measure the vapor density, while light from an argon-ion laser,
array of light emitting diodes, or discharge lamp is used for desorption.
Potassium is found to exhibit significantly weaker LIAD from paraffin compared
to Rb and Cs, and we were unable to observe LIAD with sodium. A simple LIAD
model is applied to describe the observed vapor-density dynamics, and the role
of the cell's stem is explored through the use of cells with lockable stems.
Stabilization of Cs vapor density above its equilibrium value over 25 minutes
is demonstrated. The results of this work could be used to assess the use of
LIAD for vapor-density control in magnetometers, clocks, and gyroscopes
utilizing coated cells.Comment: 10 pages, 11 figure