2,677 research outputs found
Tuning p-wave interactions in an ultracold Fermi gas of atoms
We have measured a p-wave Feshbach resonance in a single-component, ultracold
Fermi gas of potassium atoms. We have used this resonance to enhance the
normally suppressed p-wave collision cross-section to values larger than the
background s-wave cross-section between potassium atoms in different
spin-states. In addition to the modification of two-body elastic processes, the
resonance dramatically enhances three-body inelastic collisional loss.Comment: 4 pages, 5 figure
Reconstruction of eye movements during blinks
In eye movement research in reading, the amount of data plays a crucial role
for the validation of results. A methodological problem for the analysis of the
eye movement in reading are blinks, when readers close their eyes. Blinking
rate increases with increasing reading time, resulting in high data losses,
especially for older adults or reading impaired subjects. We present a method,
based on the symbolic sequence dynamics of the eye movements, that reconstructs
the horizontal position of the eyes while the reader blinks. The method makes
use of an observed fact that the movements of the eyes before closing or after
opening contain information about the eyes movements during blinks. Test
results indicate that our reconstruction method is superior to methods that use
simpler interpolation approaches. In addition, analyses of the reconstructed
data show no significant deviation from the usual behavior observed in readers
Chaotic Orbits in Thermal-Equilibrium Beams: Existence and Dynamical Implications
Phase mixing of chaotic orbits exponentially distributes these orbits through
their accessible phase space. This phenomenon, commonly called ``chaotic
mixing'', stands in marked contrast to phase mixing of regular orbits which
proceeds as a power law in time. It is operationally irreversible; hence, its
associated e-folding time scale sets a condition on any process envisioned for
emittance compensation. A key question is whether beams can support chaotic
orbits, and if so, under what conditions? We numerically investigate the
parameter space of three-dimensional thermal-equilibrium beams with space
charge, confined by linear external focusing forces, to determine whether the
associated potentials support chaotic orbits. We find that a large subset of
the parameter space does support chaos and, in turn, chaotic mixing. Details
and implications are enumerated.Comment: 39 pages, including 14 figure
Autler-Townes splitting in two-color photoassociation of 6Li
We report on high-resolution two-color photoassociation spectroscopy in the
triplet system of magneto-optically trapped 6Li. The absolute transition
frequencies have been measured. Strong optical coupling of the bound molecular
states has been observed as Autler-Townes splitting in the photoassociation
signal. The spontaneous bound-bound transition rate is determined and the
molecule formation rate is estimated. The observed lineshapes are in good
agreement with the theoretical model.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. A (Rapid
Communication
OH hyperfine ground state: from precision measurement to molecular qubits
We perform precision microwave spectroscopy--aided by Stark deceleration--to
reveal the low magnetic field behavior of OH in its ^2\Pi_{3/2} ro-vibronic
ground state, identifying two field-insensitive hyperfine transitions suitable
as qubits and determining a differential Lande g-factor of
1.267(5)\times10^{-3} between opposite parity components of the
\Lambda-doublet. The data are successfully modeled with an effective hyperfine
Zeeman Hamiltonian, which we use to make a tenfold improvement of the
magnetically sensitive, astrophysically important \Delta F=\pm1 satellite-line
frequencies, yielding 1720529887(10) Hz and 1612230825(15) Hz.Comment: 4+ pages, 3 figure
How Does a Dipolar Bose-Einstein Condensate Collapse?
We emphasize that the macroscopic collapse of a dipolar Bose-Einstein
condensate in a pancake-shaped trap occurs through local density fluctuations,
rather than through a global collapse to the trap center. This hypothesis is
supported by a recent experiment in a chromium condensate.Comment: Proceedings of 17th International Laser Physics Worksho
A Dielectric Superfluid of Polar Molecules
We show that, under achievable experimental conditions, a Bose-Einstein
condensate (BEC) of polar molecules can exhibit dielectric character. In
particular, we derive a set of self-consistent mean-field equations that couple
the condensate density to its electric dipole field, leading to the emergence
of polarization modes that are coupled to the rich quasiparticle spectrum of
the condensate. While the usual roton instability is suppressed in this system,
the coupling can give rise to a phonon-like instability that is characteristic
of a dielectric material with a negative static dielectric function.Comment: Version published in New Journal of Physics, 11+ pages, 4 figure
Candidate molecular ions for an electron electric dipole moment experiment
This paper is a theoretical work in support of a newly proposed experiment
(R. Stutz and E. Cornell, Bull. Am. Soc. Phys. 89, 76 2004) that promises
greater sensitivity to measurements of the electron's electric dipole moment
(EDM) based on the trapping of molecular ions. Such an experiment requires the
choice of a suitable molecule that is both experimentally feasible and
possesses an expectation of a reasonable EDM signal. We find that the molecular
ions PtH+, HfH+, and HfF+ are suitable candidates in their low-lying triplet
Delta states. In particular, we anticipate that the effective electric fields
generated inside these molecules are approximately of 73 GV/cm, -17 GV/cm, and
-18 GV/cm respectively. As a byproduct of this discussion, we also explain how
to make estimates of the size of the effective electric field acting in a
molecule, using commercially available, nonrelativistic molecular structure
software.Comment: 25 pages, 3 figures, submitted to Physical Review
Ultracold collisions of oxygen molecules
Collision cross sections and rate constants between two ground- state oxygen
molecules are investigated theoretically at translational energies below K and in zero magnetic field. We present calculations for elastic and spin-
changing inelastic collision rates for different isotopic combinations of
oxygen atoms as a prelude to understanding their collisional stability in
ultracold magnetic traps. A numerical analysis has been made in the framework
of a rigid- rotor model that accounts fully for the singlet, triplet, and
quintet potential energy surfaces in this system. The results offer insights
into the effectiveness of evaporative cooling and the properties of molecular
Bose- Einstein condensates, as well as estimates of collisional lifetimes in
magnetic traps. Specifically, looks like a good candidate for
ultracold studies, while is unlikely to survive evaporative
cooling. Since is representative of a wide class of molecules that
are paramagnetic in their ground state we conclude that many molecules can be
successfully magnetically trapped at ultralow temperatures.Comment: 15 pages, 9 figure
Precision Spectroscopy of Polarized Molecules in an Ion Trap
Polar molecules are desirable systems for quantum simulations and cold
chemistry. Molecular ions are easily trapped, but a bias electric field applied
to polarize them tends to accelerate them out of the trap. We present a general
solution to this issue by rotating the bias field slowly enough for the
molecular polarization axis to follow but rapidly enough for the ions to stay
trapped. We demonstrate Ramsey spectroscopy between Stark-Zeeman sublevels in
180Hf19F+ with a coherence time of 100 ms. Frequency shifts arising from
well-controlled topological (Berry) phases are used to determine magnetic
g-factors. The rotating-bias-field technique may enable using trapped polar
molecules for precision measurement and quantum information science, including
the search for an electron electric dipole moment.Comment: Accepted to Scienc
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