aktualisiertes pdf - DPG-Tagungen

Spinzustandes freigesetzt. Der Streuquerschnitt für diese Stoßprozesse
ist unabhängig vom Molekülpotential und skaliert mit dem magnetischen
Moment µ der Stoßpartner in der dritten Potenz. Bei Chrom
(µ = 6 · µB) wurden dipolare Relaxationsraten von 4 · 10 −12 cm 3 /s bis
3.2 · 10 −11 cm 3 /s bei Magnetfeldern von 1G bis 44G gemessen. Die dadurch
entstehenden Verluste verhindern die Bose-Einstein-Kondensation
von Chrom in einer magnetischen Falle.[1]
Wir präsentieren ein auf der dipolaren Kopplung zweier Spins beruhendes
theoretisches Modell zur Berechnung der dipolaren Relaxationsrate,
welches einfach auf andere dipolare Gase übertragen werden kann, sowie
vergleichende Messungen an Chrom, die dieses Modell experimentell
bestätigen.
[1] S. Hensler et al., ” Dipolar Relaxation in an ultra-cold Gas of magnetically
trapped chromium atoms“, Appl. Phys. B, 77 (8), 765 (2003)
Q 27.6 Di 17:45 HS 224
Cold heteronuclear alkali dimers (LiCs, NaCs) attached
to helium nanodroplets — •M. Mudrich 1 , O. Bünermann 2 ,
F. Stienkemeier 2 , and M. Weidemüller 1 — 1 Physikalisches
Institut, Universität Freiburg, 79104 Freiburg — 2 Fakultät für Physik,
Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld
Cold heteronuclear alkali dimers (LiCs and NaCs) are formed in a
beam of helium nanodroplets. Excitation spectra in the frequency range
of a tunable Ti:Sa-laser are recorded using mass-selective photoionization,
laser-induced fluorescence and laser-induced beam depletion as detection
methods. The observed vibrational progressions are identified in
terms of transitions within the triplet manifold. Analysis of the spectra
yields constraints to ab initio potential curves from literature. Laserinduced
desorption of the heteronuclear dimers is observed which opens
perspectives to create a beam of free, cold heteronuclear molecules for
precision spectroscopy or to provide a source for deceleration and trapping
of polar molecules.
Q 27.7 Di 18:00 HS 224
Saturation of the Photoassociation of Ultracold Molecules in
an Optical Dipole Trap — •Roland Wester, Stephan Kraft,
Marcel Mudrich, Matthias Staudt, Jörg Lange, and Matthias
Weidemüller — Physikalisches Institut, Universität Freiburg, 79104
Freiburg
We trap Cesium atoms in a quasi-electrostatic trap (QUEST) formed
by the focus of a CO2-Laser. Photoassociation is induced by a tunable
Titanium-Sapphire laser and is currently monitored by measuring
trapped atom losses. The sensitivity of this approach allowed us to measure
the Franck-Condon factors for transitions into the lowest vibrational
levels of the 0 − g
Q 28 Quantengase III
state. Saturation of the photoassoaciation is observed
both due to depletion of the trapped atomic sample and due to strong
coupling of the scattering state to bound molecular states. These processes
are disentangled and the results are compared to the photoassociation
model by Bohn and Julienne. The photoassociation rate coefficient
is found to saturate at the unitarity limit.
Q 27.8 Di 18:15 HS 224
Two-dimensional trapping of dipolar molecules in time-varying
electric fields — •T. Junglen, T. Rieger, S.A. Rangwala,
P.W.H. Pinkse, and G. Rempe — Max-Planck-Institut für
Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching
Cold molecular samples offer new perspectives in atomic and molecular
physics, in particular high-precision measurements and collisional physics
studies. These fields would benefit from new methods to produce and manipulate
such samples. Recently, we have obtained two-dimensional trapping
of low-field seeking polar molecules in electrostatic fields[1]. However,
high-field seeking molecules cannot be trapped as Maxwell’s equations
do not allow free-space maxima in electrostatic fields. We here report
on two-dimensional trapping of cold dipolar molecules in an electrodynamic
trap[2]. Slow ND3 molecules from an effusive source are guided
between four 50cm long rods driven by an alternating electric potential
at frequencies of a few kHz. With this method a trapping potential of
the order of 10mK can be obtained for low-field seeking states, slightly
less for high-field seeking states.
[1] S.A. Rangwala et al., Phys. Rev. A 67, 043406 (2003)
[2] T. Junglen et al., ArXiv:Physics/0310046
Zeit: Dienstag 16:30–18:30 Raum: HS 225
Q 28.1 Di 16:30 HS 225
Ultrakalte Bose-Gase in optischen Gittern — •Thomas Schulte,
Sascha Drenkelforth, Carsten Klempt, Wolfgang Ertmer
und Jan Arlt — Institut für Quantenoptik; Universität Hannover;
Welfengarten 1; 30167 Hannover
Optische Potentiale, insbesondere optische Gitter haben sich in den
letzten Jahren zu einem wertvollen Werkzeug zur Untersuchung ultrakalter
Quantengase entwickelt. Die erreichbaren Potentialtiefen sowie
die Größe der Fallenfrequenzen erlauben Untersuchungen in bisher unzugänglichen
Regimen in denen starke Korrelationen das System dominieren
können.
Insbesondere eignen sich optische Potentiale zum Studium niederdimensionaler
Systeme. Von großem Interesse ist hierbei die Untersuchung
eindimensionaler Quantengase in einem 2D-optischen Gitter.
In Abhängigkeit von den experimentellen Parametern, können solche
eindimensionalen Quantengase durch starke Korrelationen geprägt sein
(Tonks-Gas) oder durch Meanfield-Theorien beschrieben werden (BEC).
Die physikalischen Eigenschaften des Quantengases in diesen beiden Regimen
weichen stark voneinander ab.
In diesem Vortrag berichten wir über den Stand unserer Arbeiten mit
ultrakalten Rb-Atomen in optischen Gittern. Wir stellen den mit unserem
Experiment erreichbaren Parameterbereich, insbesondere mit Blick auf
die Erzeugung stark korrelierter Systeme dar und stellen die erreichten
Resultate sowie unsere Projekte in quasi-periodischen optischen Gittern
vor.
109
Q 28.2 Di 16:45 HS 225
Inhomogeneous Bose-Fermi mixtures in regular lattices —
•M. Cramer 1 , J. Eisert 1 , and F. Illuminati 2 — 1 Institut für
Physik, Universität Potsdam, Am Neuen Palais 10, D-14469 Potsdam —
2 Dipartimento di Fisica, Università di Salerno, INFM UdR di Salerno,
I-84081 Baronissi (SA)
We determine ground state properties of inhomogeneous boson-fermion
mixtures in regular lattices by studying the Bose-Fermi Hubbard model
with the inclusion of confining external potentials. We present the exact
solution in the limit of vanishing hopping (ultradeep lattices) and study
the resulting domain structure of composite particles. Finite hopping is
introduced in the framework of mean field theory and perturbative corrections.
We determine the domain boundaries between Mott-insulator
and hopping-dominated regions for lattices of arbitrary dimensionality
within Landau theory. The results are compared with a numerical analysis
based on a Gutzwiller variational approach.
Q 28.3 Di 17:00 HS 225
Spatial correlations of trapped 1d bosons in an optical lattice
— •Corinna Kollath 1 , Ulrich Schollwöck 1 , Jan von Delft 1 ,
and Wilhelm Zwerger 1,2 — 1 LMU-München, Theresienstr. 37, 80333
München — 2 Institut für theoretische Physik, Universität Innsbruck,
Thechnikerstr. 25, 6020 Innsbruck
Greiner et al.[1] succeeded in driving a quantum phase transition between
a superfluid and a Mott-insulating phase of trapped cold bosonic
atoms in an optical lattice. We investigate a similar quasi-one dimensional
system by using the density matrix renormalization group to study the
Bose-Hubbard model at T = 0 for experimentally realistic numbers of
lattice sites [3] (for experiments on quasi-one dimensional systems see
[2]). We focus on the influence of the parabolic trapping on the quantum