247 research outputs found
Hyperfine, rotational and Zeeman structure of the lowest vibrational levels of the Rb \tripletex state
We present the results of an experimental and theoretical study of the
electronically excited \tripletex state of Rb molecules. The
vibrational energies are measured for deeply bound states from the bottom up to
using laser spectroscopy of ultracold Rb Feshbach molecules. The
spectrum of each vibrational state is dominated by a 47\,GHz splitting into a
\cog and \clg component caused mainly by a strong second order spin-orbit
interaction. Our spectroscopy fully resolves the rotational, hyperfine, and
Zeeman structure of the spectrum. We are able to describe to first order this
structure using a simplified effective Hamiltonian.Comment: 10 pages, 7 figures, 2 table
Very long storage times and evaporative cooling of cesium atoms in a quasi-electrostatic dipole trap
We have trapped cesium atoms over many minutes in the focus of a CO-laser
beam employing an extremely simple laser system. Collisional properties of the
unpolarized atoms in their electronic ground state are investigated. Inelastic
binary collisions changing the hyperfine state lead to trap loss which is
quantitatively analyzed. Elastic collisions result in evaporative cooling of
the trapped gas from 25 K to 10 K over a time scale of about 150 s.Comment: 5 pages, 3 figure
Suppression of inhomogeneous broadening in rf spectroscopy of optically trapped atoms
We present a novel method for reducing the inhomogeneous frequency broadening
in the hyperfine splitting of the ground state of optically trapped atoms. This
reduction is achieved by the addition of a weak light field, spatially
mode-matched with the trapping field and whose frequency is tuned in-between
the two hyperfine levels. We experimentally demonstrate the new scheme with Rb
85 atoms, and report a 50-fold narrowing of the rf spectrum
Quantum entanglement using trapped atomic spins
We propose an implementation for quantum logic and computing using trapped
atomic spins of two different species, interacting via direct magnetic
spin-spin interaction. In this scheme, the spins (electronic or nuclear) of
distantly spaced trapped neutral atoms serve as the qubit arrays for quantum
information processing and storage, and the controlled interaction between two
spins, as required for universal quantum computing, is implemented in a three
step process that involves state swapping with a movable auxiliary spin.Comment: minor revisions with an updated discussion on adibatic tranportation
of trapped qubit, 5 pages, 3 figs, resubmitted to PR
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
Sympathetic Cooling with Two Atomic Species in an Optical Trap
We simultaneously trap ultracold lithium and cesium atoms in an optical
dipole trap formed by the focus of a CO laser and study the exchange of
thermal energy between the gases. The cesium gas, which is optically cooled to
K, efficiently decreases the temperature of the lithium gas through
sympathetic cooling. The measured cross section for thermalizing
Cs-Li collisions is cm, for both species in
their lowest hyperfine ground state. Besides thermalization, we observe
evaporation of lithium purely through elastic cesium-lithium collisions
(sympathetic evaporation).Comment: 4 pages 3 fig
Molecular Dynamics Simulation of Sympathetic Crystallization of Molecular Ions
It is shown that the translational degrees of freedom of a large variety of
molecules, from light diatomic to heavy organic ones, can be cooled
sympathetically and brought to rest (crystallized) in a linear Paul trap. The
method relies on endowing the molecules with an appropriate positive charge,
storage in a linear radiofrequency trap, and sympathetic cooling. Two
well--known atomic coolant species, and
, are sufficient for cooling the molecular mass range
from 2 to 20,000 amu. The large molecular charge required for simultaneous
trapping of heavy molecules and of the coolant ions can easily be produced
using electrospray ionization. Crystallized molecular ions offer vast
opportunities for novel studies.Comment: Accepted for publication in Phys. Rev.
All-Optical Production of a Degenerate Fermi Gas
We achieve degeneracy in a mixture of the two lowest hyperfine states of
Li by direct evaporation in a CO laser trap, yielding the first
all-optically produced degenerate Fermi gas. More than atoms are
confined at temperatures below K at full trap depth, where the Fermi
temperature for each state is K. This degenerate two-component mixture
is ideal for exploring mechanisms of superconductivity ranging from Cooper
pairing to Bose condensation of strongly bound pairs.Comment: 4 pgs RevTeX with 2 eps figs, to be published in Phys. Rev. Let
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