105 research outputs found
Atom-molecule collisions in an optically trapped gas
Cold inelastic collisions between confined cesium (Cs) atoms and Cs
molecules are investigated inside a CO laser dipole trap. Inelastic
atom-molecule collisions can be observed and measured with a rate coefficient
of cm s, mainly independent of the
molecular ro-vibrational state populated. Lifetimes of purely atomic and
molecular samples are essentially limited by rest gas collisions. The pure
molecular trap lifetime ranges 0,3-1 s, four times smaller than the atomic one,
as is also observed in a pure magnetic trap. We give an estimation of the
inelastic molecule-molecule collision rate to be cm
s
Proof-of-principle demonstration of vertical gravity gradient measurement using a single proof mass double-loop atom interferometer
We demonstrate a proof-of-principle of direct Earth gravity gradient
measurement with an atom interferometer-based gravity gradiomter using a single
proof mass of cold 87 rubidium atoms. The atomic gradiometer is implemented in
the so-called double-loop configuration, hence providing a direct gravity
gradient dependent phase shift insensitive do DC acceleration and constant
rotation rate. The atom interferometer (AI) can be either operated as a
gravimeter or a gradiomter by simply adding an extra Raman -pulse. We
demonstrate gravity gradient measurements first using a vibration isolation
platform and second without seismic isolation using the correlation between the
AI signal and the vibration signal measured by an auxilliary classical
accelerometer. The simplicity of the experimental setup (a single atomic source
and unique detection) and the immunity of the AI to rotation-induced contrast
loss, make it a good candidate for onboard gravity gradient measurements.Comment: 11 pages, 7 figure
New concepts of inertial measurements with multi-species atom interferometry
In the field of cold atom inertial sensors, we present and analyze innovative
configurations for improving their measurement range and sensitivity,
especially attracting for onboard applications. These configurations rely on
multi-species atom interferometry, involving the simultaneous manipulation of
different atomic species in a unique instrument to deduce inertial
measurements. Using a dual-species atom accelerometer manipulating
simultaneously both isotopes of rubidium, we report a preliminary experimental
realization of original concepts involving the implementation of two atom
interferometers first with different interrogation times and secondly in phase
quadrature. These results open the door to a new generation of atomic sensors
relying on high performance multi-species atom interferometric measurements
Local gravity measurement with the combination of atom interferometry and Bloch oscillations
We present a local measurement of gravity combining Bloch oscillations and
atom interferometry. With a falling distance of 0.8 mm, we achieve a
sensitivity of 2x10-7 g with an integration time of 300 s. No bias associated
with the Bloch oscillations has been measured. A contrast decay with Bloch
oscillations has been observed and attributed to the spatial quality of the
laser beams. A simple experimental configuration has been adopted where a
single retro-reflected laser beam is performing atoms launch, stimulated Raman
transitions and Bloch oscillations. The combination of Bloch oscillations and
atom interferometry can thus be realized with an apparatus no more complex than
a standard atomic gravimeter
Experimental investigation of ultracold atom-molecule collisions
Ultracold collisions between Cs atoms and Cs2 dimers in the electronic ground
state are observed in an optically trapped gas of atoms and molecules. The Cs2
molecules are formed in the triplet ground state by cw-photoassociation through
the outer well of the 0g-(P3/2) excited electronic state. Inelastic
atom-molecule collisions converting internal excitation into kinetic energy
lead to a loss of Cs2 molecules from the dipole trap. Rate coefficients are
determined for collisions involving Cs atoms in either the F=3 or F=4 hyperfine
ground state and Cs2 molecules in either highly vibrationally excited states
(v'=32-47) or in low vibrational states (v'=4-6) of the a ^3 Sigma_u^+ triplet
ground state. The rate coefficients beta ~10^{-10} cm^3/s are found to be
largely independent of the vibrational and rotational excitation indicating
unitary limited cross sections.Comment: 4 pages, 3 figures, submitted for publicatio
Star clusters dynamics in a laboratory: electrons in an ultracold plasma
Electrons in a spherical ultracold quasineutral plasma at temperature in the
Kelvin range can be created by laser excitation of an ultra-cold laser cooled
atomic cloud. The dynamical behavior of the electrons is similar to the one
described by conventional models of stars clusters dynamics. The single mass
component, the spherical symmetry and no stars evolution are here accurate
assumptions. The analog of binary stars formations in the cluster case is
three-body recombination in Rydberg atoms in the plasma case with the same
Heggie's law: soft binaries get softer and hard binaries get harder. We
demonstrate that the evolution of such an ultracold plasma is dominated by
Fokker-Planck kinetics equations formally identical to the ones controlling the
evolution of a stars cluster. The Virial theorem leads to a link between the
plasma temperature and the ions and electrons numbers. The Fokker-Planck
equation is approximate using gaseous and fluid models. We found that the
electrons are in a Kramers-Michie-King's type quasi-equilibrium distribution as
stars in clusters. Knowing the electron distribution and using forced fast
electron extraction we are able to determine the plasma temperature knowing the
trapping potential depth.Comment: Submitted to MNRA
Zero-velocity atom interferometry using a retroreflected frequency chirped laser
International audienceAtom interferometry using stimulated Raman transitions in a retroreflected configuration is the first choice in high-precision measurements because it provides low phase noise, a high-quality Raman wave front, and a simple experimental setup. However, it cannot be used for atoms at zero velocity because two pairs of Raman lasers are simultaneously resonant. Here we report a method which allows this degeneracy to be lifted by using a frequency chirp on the Raman lasers. Using this technique, we realize a Mach-Zehnder atom interferometer hybridized with a force balanced accelerometer which provides horizontal acceleration measurements with a short-term sensitivity of 3.2×10−5ms−2/Hz. This technique could be used for multiaxis inertial sensors, tiltmeters, or atom interferometry in a microgravity environment
I.C.E.: An Ultra-Cold Atom Source for Long-Baseline Interferometric Inertial Sensors in Reduced Gravity
The accuracy and precision of current atom-interferometric inertialsensors
rival state-of-the-art conventional devices using artifact-based test masses .
Atomic sensors are well suited for fundamental measurements of gravito-inertial
fields. The sensitivity required to test gravitational theories can be achieved
by extending the baseline of the interferometer. The I.C.E.
(Interf\'erom\'etrie Coh\'erente pour l'Espace) interferometer aims to achieve
long interrogation times in compact apparatus via reduced gravity. We have
tested a cold-atom source during airplane parabolic flights. We show that this
environment is compatible with free-fall interferometric measurements using up
to 4 second interrogation time. We present the next-generation apparatus using
degenerate gases for low release-velocity atomic sources in space-borne
experiments
- …