193 research outputs found
Reservoir spectroscopy of 5s5p P - 5sd D transitions in strontium
We perform spectroscopy on the optical dipole transitions 5s5p P -
5sd D, , for all stable isotopes of atomic
strontium. We develop a new spectroscopy scheme, in which atoms in the
metastable P state are stored in a reservoir before being probed. The
method presented here increases the attained precision and accuracy by two
orders of magnitude compared to similar experiments performed in a
magneto-optical trap or discharge. We show how the state distribution and
velocity spread of atoms in the reservoir can be tailored to increase the
spectroscopy performance. The absolute transition frequencies are measured with
an accuracy of 2 MHz. The isotope shifts are given to within 200 kHz. We
calculate the and parameters for the hyperfine structure of the
fermionic isotope at the MHz-level. Furthermore, we investigate the branching
ratios of the D states into the P states and discuss
immediate implications on schemes of optical pumping and fluorescence
detection.Comment: 15 pages, 7 figures, 4 table
Degenerate quantum gases of strontium
Degenerate quantum gases of alkaline-earth-like elements open new
opportunities in research areas ranging from molecular physics to the study of
strongly correlated systems. These experiments exploit the rich electronic
structure of these elements, which is markedly different from the one of other
species for which quantum degeneracy has been attained. Specifically,
alkaline-earth-like atoms, such as strontium, feature metastable triplet
states, narrow intercombination lines, and a non-magnetic, closed-shell ground
state. This review covers the creation of quantum degenerate gases of strontium
and the first experiments performed with this new system. It focuses on
laser-cooling and evaporation schemes, which enable the creation of
Bose-Einstein condensates and degenerate Fermi gases of all strontium isotopes,
and shows how they are used for the investigation of optical Feshbach
resonances, the study of degenerate gases loaded into an optical lattice, as
well as the coherent creation of Sr_2 molecules.Comment: Review paper, 43 pages, 24 figures, 249 reference
Creation of ultracold Sr2 molecules in the electronic ground state
We report on the creation of ultracold 84Sr2 molecules in the electronic
ground state. The molecules are formed from atom pairs on sites of an optical
lattice using stimulated Raman adiabatic passage (STIRAP). We achieve a
transfer efficiency of 30% and obtain 4x10^4 molecules with full control over
the external and internal quantum state. STIRAP is performed near the narrow
1S0-3P1 intercombination transition, using a vibrational level of the 0u
potential as intermediate state. In preparation of our molecule association
scheme, we have determined the binding energies of the last vibrational levels
of the 0u, 1u excited-state, and the 1\Sigma_g^+ ground-state potentials. Our
work overcomes the previous limitation of STIRAP schemes to systems with
Feshbach resonances, thereby establishing a route that is applicable to many
systems beyond bi-alkalis.Comment: 7 pages, 7 figures, 3 table
Bose-Einstein condensation of 86Sr
We report on the attainment of Bose-Einstein condensation of 86Sr. This
isotope has a scattering length of about +800 a0 and thus suffers from fast
three-body losses. To avoid detrimental atom loss, evaporative cooling is
performed at low densities around 3x10^12 cm^-3 in a large volume optical
dipole trap. We obtain almost pure condensates of 5x10^3 atoms.Comment: 4 pages, 3 figure
Soft Sphere Packings at Finite Pressure but Unstable to Shear
When are athermal soft sphere packings jammed ? Any experimentally relevant
definition must at the very least require a jammed packing to resist shear. We
demonstrate that widely used (numerical) protocols in which particles are
compressed together, can and do produce packings which are unstable to shear -
and that the probability of generating such packings reaches one near jamming.
We introduce a new protocol that, by allowing the system to explore different
box shapes as it equilibrates, generates truly jammed packings with strictly
positive shear moduli G. For these packings, the scaling of the average of G is
consistent with earlier results, while the probability distribution P(G)
exhibits novel and rich scalingComment: 5 pages, 6 figures. Resubmitted to Physical Review Letters after a
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