107 research outputs found
Pulsed pumping of a Bose-Einstein condensate
In this work, we examine a system for coherent transfer of atoms into a
Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein
condensates in different hyperfine ground states held in the same dc magnetic
trap. By means of a pulsed transfer of atoms, we are able to show a clear
resonance in the timing of the transfer, both in temperature and number, from
which we draw conclusions about the underlying physical process. The results
are discussed in the context of the recently demonstrated pumped atom laser.Comment: 5 pages, 5 figures, published in Physical Review
Rb-85 tunable-interaction Bose-Einstein condensate machine
We describe our experimental setup for creating stable Bose-Einstein
condensates of Rb-85 with tunable interparticle interactions. We use
sympathetic cooling with Rb-87 in two stages, initially in a tight
Ioffe-Pritchard magnetic trap and subsequently in a weak, large-volume crossed
optical dipole trap, using the 155 G Feshbach resonance to manipulate the
elastic and inelastic scattering properties of the Rb-85 atoms. Typical Rb-85
condensates contain 4 x 10^4 atoms with a scattering length of a=+200a_0. Our
minimalist apparatus is well-suited to experiments on dual-species and spinor
Rb condensates, and has several simplifications over the Rb-85 BEC machine at
JILA (Papp, 2007; Papp and Wieman, 2006), which we discuss at the end of this
article.Comment: 10 pages, 8 figure
Nonadiabatic transitions in the exit channel of atom-molecule collisions: Fine-structure branching in Na+N[sub 2]
We study Na+Nâcollisions by laser excitation of the collision complex in a differential scattering experiment. The measured relative population of the Na(3p) fine-structure levels reflects the nonadiabatic transitions occuring in the exit channel of the collision.Theoretical results obtained with a classical-path formalism and accurate quantum chemical data for NaNâ are found to be in good agreement. The presence of a conical intersection for the T-shaped geometry has a profound influence on the observed fine-structure branching.Support from the Deutsche Forschungsgemeinschaft is
gratefully acknowledged
A pumped atom laser
We present the experimental realization of a pumped atom laser. We
demonstrate the pumping through measurements of the source and laser-mode atom
numbers, making a rate equation study of the pumping process.Comment: Version 2 contains 18 pages and 4 figures. We have significantly
rewritten the introduction, as well as including a discussion of Rayleigh and
Raman superradiant scattering and how these relate to continuous pumping of
an atom laser. Five new references were adde
Collision photography: polarization imaging of atom-molecule collisions
We report differential scattering experiments on the laser excitation of Na+Mcollision pairs with M=Nâ, CO, CâHâ, and COâ. The collision event is probed by the laser polarization revealing geometric and electronic properties of the collision pair. The experimental data are compared to the results of a Monte Carlo trajectory simulation using ab initio quantum chemical data.Financial support from the Deutsche Forschungsgemeinschaft
and the Schweizerischer Nationalfond (Project No. 20-
065290.01) is gratefully acknowledged
Using Insights from Cognitive Neuroscience to Investigate the Effects of Event-Driven Process Chains on Process Model Comprehension
Business process models have been adopted by enterprises for more than a decade. Especially for domain experts, the comprehension of process models constitutes a challenging task that needs to be mastered when creating or reading these models. This paper presents the results we obtained from an eye tracking experiment on process model comprehension. In detail, individuals with either no or advanced expertise in process modeling were confronted with models expressed in terms of Event-driven Process Chains (EPCs), reflecting different levels of difficulty. The first results of this experiment confirm recent findings from one of our previous experiments on the reading and comprehension of process models. On one hand, independent from their level of exper-tise, all individuals face similar patterns, when being confronted with process models exceeding a certain level of difficulty. On the other, it appears that process models expressed in terms of EPCs are perceived diïŹerently compared to process models speciïŹed in the Business Process Model and Notation (BPMN). In the end, their generalization needs to be conïŹrmed by additional empirical experiments. The presented expe-riment continues a series of experiments that aim to unravel the factors fostering the comprehension of business process models by using methods and theories stemming from the ïŹeld of cognitive neuroscience and psychology
Measurement of inelastic losses in a sample of ultracold Rb-85
We report on the observation and characterisation of an inelastic loss
feature in collisions between ultracold Rb-85 |F=2, m_F=-2> atoms at a magnetic
field of 220 G. Our apparatus creates ultracold Rb-85 clouds by sympathetic
cooling with a Rb-87 reservoir, and can produce pure Rb-87 condensates of 10^6
atoms by a combination of evaporative cooling in a quadrupole-Ioffe magnetic
trap and further evaporation in a weak, large-volume optical dipole trap. By
combining Rb-85 and Rb-87 atoms collected in a dual-species magneto-optical
trap and selectively evaporating the heavier isotope, we demonstrate strong
sympathetic cooling of the Rb-85 cloud, increasing its phase space density by
three orders of magnitude with no detectable loss in number. We have used
ultracold samples created in this way to observe the variation of inelastic
loss in ultracold Rb-85 as a function of magnetic field near the 155 G Feshbach
resonance. We have also measured a previously unobserved loss feature at
219.9(1) G with a width of 0.28(6) G, which we associate with a narrow Feshbach
resonance predicted by theory.Comment: 4 pages, 3 figures, content change
93. Spécificités des facteurs histopronostiques du cancer du sein de la femme trÚs ùgée : vers une approche du traitement individualisé
Video Endoscopy-Guided Intrabronchial Spray Inoculation of Mycobacterium bovis in Goats and Comparative Assessment of Lung Lesions With Various Imaging Methods
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