842 research outputs found
Continuous Loading of a Conservative Trap from an Atomic Beam
We demonstrate the fast accumulation of Cr atoms in a conservative potential
from a magnetically guided atomic beam. Without laser cooling on a cycling
transition, a single dissipative step realized by optical pumping allows to
load atoms at a rate of 2*10^7 1/s in the trap. Within less than 100 ms we
reach the collisionally dense regime, from which we directly produce a
Bose-Einstein condensate with subsequent evaporative cooling. This constitutes
a new approach to degeneracy where, provided a slow beam of particles can be
produced by some means, Bose-Einstein condensation can be reached for species
without a cycling transition.Comment: 4 pages, 4 figure
Depolarisation cooling of an atomic cloud
We propose a cooling scheme based on depolarisation of a polarised cloud of
trapped atoms. Similar to adiabatic demagnetisation, we suggest to use the
coupling between the internal spin reservoir of the cloud and the external
kinetic reservoir via dipolar relaxation to reduce the temperature of the
cloud. By optical pumping one can cool the spin reservoir and force the cooling
process. In case of a trapped gas of dipolar chromium atoms, we show that this
cooling technique can be performed continuously and used to approach the
critical phase space density for BECComment: 8 pages, 5 figure
Dietary intake of meat and meat-derived heterocyclic aromatic amines and their correlation with DNA adducts in female breast tissue
Phase Space Tomography of Matter-Wave Diffraction in the Talbot Regime
We report on the theoretical investigation of Wigner distribution function
(WDF) reconstruction of the motional quantum state of large molecules in de
Broglie interference. De Broglie interference of fullerenes and as the like
already proves the wavelike behaviour of these heavy particles, while we aim to
extract more quantitative information about the superposition quantum state in
motion. We simulate the reconstruction of the WDF numerically based on an
analytic probability distribution and investigate its properties by variation
of parameters, which are relevant for the experiment. Even though the WDF
described in the near-field experiment cannot be reconstructed completely, we
observe negativity even in the partially reconstructed WDF. We further consider
incoherent factors to simulate the experimental situation such as a finite
number of slits, collimation, and particle-slit van der Waals interaction. From
this we find experimental conditions to reconstruct the WDF from Talbot
interference fringes in molecule Talbot-Lau interferometry.Comment: 16 pages, 9 figures, accepted at New Journal of Physic
Rydberg trimers and excited dimers bound by internal quantum reflection
Quantum reflection is a pure wave phenomena that predicts reflection of a
particle at a changing potential for cases where complete transmission occurs
classically. For a chemical bond, we find that this effect can lead to
non-classical vibrational turning points and bound states at extremely large
interatomic distances. Only recently has the existence of such ultralong-range
Rydberg molecules been demonstrated experimentally. Here, we identify a broad
range of molecular lines, most of which are shown to originate from two
different novel sources: a single-photon associated triatomic molecule formed
by a Rydberg atom and two ground state atoms and a series of excited dimer
states that are bound by a so far unexplored mechanism based on internal
quantum reflection at a steep potential drop. The properties of the Rydberg
molecules identified in this work qualify them as prototypes for a new type of
chemistry at ultracold temperatures.Comment: 6 pages, 3 figures, 1 tabl
Continuous loading of a magnetic trap
We have realized a scheme for continuous loading of a magnetic trap (MT).
^{52}Cr atoms are continuously captured and cooled in a magneto-optical trap
(MOT). Optical pumping to a metastable state decouples atoms from the cooling
light. Due to their high magnetic moment (6 Bohr magnetons), low-field seeking
metastable atoms are trapped in the magnetic quadrupole field provided by the
MOT. Limited by inelastic collisions between atoms in the MOT and in the MT, we
load 10^8 metastable atoms at a rate of 10^8 atoms/s below 100 microkelvin into
the MT. After loading we can perform optical repumping to realize a MT of
ground state chromium atoms.Comment: 4 pages, 4 figures, version 2, modified references, included
additional detailed information, minor changes in figure 3 and in tex
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