



01813nas a2200169   4500008004100000245010100041210006900142260001500211490000600226520127000232100002701502700001701529700001901546700001901565700002201584856003701606       2017                        eng d00aAbove threshold scattering about a Feshbach resonance for ultracold atoms in an optical collider0 aAbove threshold scattering about a Feshbach resonance for ultrac  c2017/09/060 v83 a<p>Studies of magnetically tunable Feshbach resonances in ultracold atomic gases have predominantly been carried out in the zero collision-energy limit. Here, we explore above threshold collisions at well-defined energies in the vicinity of a narrow magnetic Feshbach resonance by means of a laser-based collider. Our experiment focuses on collisions between ground-state 87Rb atoms in the |F = 2,mF = 0i and |F = 1,mF = 1i hyperfine states, which have a known s-wave resonance at 9.040(7) G at threshold that strongly couples to inelastic channels, where 1 G = 10&minus;4 T. Using our collider we can track the magnetic field shift in resonance position as the energy is tuned. This presents a challenge due to the narrow width of the resonance in conjunction with inherent broadening mechanisms of the collider. We find, however, that the narrow Feshbach scattering feature becomes imprinted on the spatial distribution of atoms in a fashion that allows for an accurate determination of resonance position as a function of collision energy through a shift in center-of-mass position of the outgoing clouds. This shift has a dispersive line shape with a zero value at the resonance position. We obtain excellent agreement with theory on the resonance position.</p>1 aHorvath, Milena, S. J.1 aThomas, Ryan1 aTiesinga, Eite1 aDeb, Amita, B.1 aKjærgaard, Niels  uhttps://arxiv.org/abs/1704.0710901318nas a2200145   4500008004100000245008900041210006900130260001300199490000800212520084800220100002201068700001901090700002601109856003701135       2012                        eng d00aAnisotropy induced Feshbach resonances in a quantum dipolar gas of  magnetic atoms
0 aAnisotropy induced Feshbach resonances in a quantum dipolar gas   c2012/9/70 v1093 a  We explore the anisotropic nature of Feshbach resonances in the collision
between ultracold magnetic submerged-shell dysprosium atoms, which can only
occur due to couplings to rotating bound states. This is in contrast to
well-studied alkali-metal atom collisions, where most Feshbach resonances are
hyperfine induced and due to rotation-less bound states. Our novel
first-principle coupled-channel calculation of the collisions between
open-4f-shell spin-polarized bosonic dysprosium reveals a striking correlation
between the anisotropy due to magnetic dipole-dipole and electrostatic
interactions and the Feshbach spectrum as a function of an external magnetic
field. Over a 20 mT magnetic field range we predict about a dozen Feshbach
resonances and show that the resonance locations are exquisitely sensitive to
the dysprosium isotope.
1 aPetrov, Alexander1 aTiesinga, Eite1 aKotochigova, Svetlana  uhttp://arxiv.org/abs/1203.4172v101381nas a2200145   4500008004100000245007000041210006900111260001400180490000700194520093200201100002301133700001901156700002301175856003701198       2008                        eng d00aAvoided crossings between bound states of ultracold Cesium dimers0 aAvoided crossings between bound states of ultracold Cesium dimer  c2008/11/50 v783 a  We present an efficient new computational method for calculating the binding
energies of the bound states of ultracold alkali-metal dimers in the presence
of magnetic fields. The method is based on propagation of coupled differential
equations and does not use a basis set for the interatomic distance coordinate.
It is much more efficient than the previous method based on a radial basis set
and allows many more spin channels to be included. This is particularly
important in the vicinity of avoided crossings between bound states. We
characterize a number of different avoided crossings in Cs_2 and compare our
converged calculations with experimental results. Small but significant
discrepancies are observed in both crossing strengths and level positions,
especially for levels with l symmetry (rotational angular momentum L=8). The
discrepancies should allow the development of improved potential models in the
future.
1 aHutson, Jeremy, M.1 aTiesinga, Eite1 aJulienne, Paul, S.  uhttp://arxiv.org/abs/0806.2583v102281nas a2200181   4500008004100000245009200041210006900133260001500202300001600217490000700233520170600240100002101946700002201967700002401989700001902013700002302032856004402055       2004                        eng d00aAdiabatic association of ultracold molecules via magnetic field tunable  interactions
0 aAdiabatic association of ultracold molecules via magnetic field   c2004/09/14  a3457 - 35000 v373 a  We consider in detail the situation of applying a time dependent external
magnetic field to a 87Rb atomic Bose-Einstein condensate held in a harmonic
trap, in order to adiabatically sweep the interatomic interactions across a
Feshbach resonance to produce diatomic molecules. To this end, we introduce a
minimal two-body Hamiltonian depending on just five measurable parameters of a
Feshbach resonance, which accurately determines all low energy binary
scattering observables, in particular, the molecular conversion efficiency of
just two atoms. Based on this description of the microscopic collision
phenomena, we use the many-body theory of T. Koehler and K. Burnett [Phys. Rev.
A 65, 033601 (2002)] to study the efficiency of the association of molecules in
a 87Rb Bose-Einstein condensate during a linear passage of the magnetic field
strength across the 100 mT Feshbach resonance. We explore different,
experimentally accessible, parameter regimes, and compare the predictions of
Landau-Zener, configuration interaction, and two level mean field calculations
with those of the microscopic many-body approach. Our comparative studies
reveal a remarkable insensitivity of the molecular conversion efficiency with
respect to both the details of the microscopic binary collision physics and the
coherent nature of the Bose-Einstein condensed gas, provided that the magnetic
field strength is varied linearly. We provide the reasons for this universality
of the molecular production achieved by linear ramps of the magnetic field
strength, and identify the Landau-Zener coefficient determined by F.H. Mies et
al. [Phys. Rev. A 61, 022721 (2000)] as the main parameter that controls the
efficiency.
1 aGoral, Krzysztof1 aKoehler, Thorsten1 aGardiner, Simon, A.1 aTiesinga, Eite1 aJulienne, Paul, S.  uhttp://arxiv.org/abs/cond-mat/0312178v5