263 research outputs found
Благотворительность элит
Deze handreiking is bedoeld als een hulpmiddel voor het gesprek binnen de opleiding, of bijvoorbeeld een faculteit, school of academie. Het gesprek kan nieuwe ideeën opleveren om de cultuur van excellentie te bevorderen. Het kan er ook toe leiden dat er tegenstrijdigheden worden gesignaleerd in de bestaande situatie die veranderd zouden moeten worden. Het is geen handleiding om stap voor stap tot een cultuur van excellentie te komen. Het kan wel leiden tot nieuwe ideeën en verbetermaatregelen. Daarom sluit elk hoofdstuk af met de vraag: wat gaan we doen? Door aandacht te geven aan deze vraag leidt het gesprek tot verandering
Collisional cooling of ultra-cold atom ensembles using Feshbach resonances
We propose a new type of cooling mechanism for ultra-cold fermionic atom
ensembles, which capitalizes on the energy dependence of inelastic collisions
in the presence of a Feshbach resonance. We first discuss the case of a single
magnetic resonance, and find that the final temperature and the cooling rate is
limited by the width of the resonance. A concrete example, based on a p-wave
resonance of K, is given. We then improve upon this setup by using both
a very sharp optical or radio-frequency induced resonance and a very broad
magnetic resonance and show that one can improve upon temperatures reached with
current technologies.Comment: 4 pages, 3 figure
Light forces in ultracold photoassociation
We study the time-resolved photoassociation of ultracold sodium in an optical
dipole trap. The photoassociation laser excites pairs of atoms to molecular
states of large total angular momentum at high intensities (above 20
kW/cm). Such transitions are generally suppressed at ultracold
temperatures by the centrifugal barriers for high partial waves. Time-resolved
ionization measurements reveal that the atoms are accelerated by the dipole
potential of the photoassociation beam. We change the collision energy by
varying the potential depth, and observe a strong variation of the
photoassociation rate. These results demonstrate the important role of light
forces in cw photoassociation at high intensities.Comment: 7 pages, 3 figure
Detecting paired and counterflow superfluidity via dipole oscillations
We suggest an experimentally feasible procedure to observe paired and
counterflow superfluidity in ultra-cold atom systems. We study the time
evolution of one-dimensional mixtures of bosonic atoms in an optical lattice
following an abrupt displacement of an additional weak confining potential. We
find that the dynamic responses of the paired superfluid phase for attractive
inter-species interactions and the counterflow superfluid phase for repulsive
interactions are qualitatively distinct and reflect the quasi long-range order
that characterizes these states. These findings suggest a clear experimental
procedure to detect these phases, and give an intuitive insight into their
dynamics.Comment: 4 pages,5 figure
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