Vorträge im SS 2012

Prof. Dr. Thomas Müller, Institut für Experimentelle Kernphysik, Karlsruhe

Der Large Hadron Collider am CERN: Dem Urknall auf der Spur (26. Juni 2012)

Am Europäischen Zentrum für Teilchenphysik CERN hat der größte und leistungsfähigste Teilchenbeschleuniger der Welt, der Large Hadron Collider LHC seine Datennahme aufgenommen. Er kollidiert Protonen oder schwere Ionen bei höchsten Energien gegeneinander, um Energiedichten und Zustände wie im frühesten Universum zu schaffen und nach neuen Teilchen und Kräften zu suchen. Besonderes Interesse gilt der Frage nach dem Ursprung der Masse, für die nach gängiger Vorstellung das Higgs-Boson verantwortlich sein soll, sowie nach Elementarteilchen, wie sie auch in Form von Dunkler Materie im Universum beobachtet werden. In diesem Vortrag werden über die wissenschaftliche Fragestellung und die experimentellen Methoden, mit denen nach diesen Teilchen gefahndet werden soll, referiert und aktuelle Resultate gezeigt.
 
Prof. Dr. Andreas Stierle, DESY und Universität Hamburg

The Atomic Structure of Nano-Objects: What X-Rays Can Tell (12. Juni 2012)

The atomic structure determination of nano-objects with dimensions in the sub-100 nm regime is a formidable task for today’s diffraction, imaging and scanning probe techniques. Such a detailed structural and compositional analysis is mandatory for a correlation with the nano-object’s functionality e.g. as heterogeneous catalysts, magnetic storage material or light emitting device. In conventional x-ray diffraction experiments on powder samples the structural analysis is hampered by a random nanoparticle orientation and often by background scattering from the supporting material. Recently, progress has been made in x-ray diffraction from single nanoparticles in the size regime of a few 100 nm allowing a reconstruction of the particle structure with a few tenth of nm resolution. Here I will present different ensemble averaging in-situ synchrotron radiation based x-ray diffraction schemes delivering quantitative information on the nanoparticle size, shape and facet surface structures under varying gas surroundings: first I will discuss high resolution reciprocal space mapping from epitaxial Rh nanoparticles under oxidizing and reducing conditions. As a second approach I will present a combinatorial high energy x-ray diffraction scheme (85 keV photon energy) allowing a systematical screening of particle size or composition under identical reaction conditions. Finally, I will demonstrate how graphene templated growth of nanoparticles with diameter < 2 nm opens the door for x-ray diffraction experiments with high crystallographic precision.
 
Prof. Dr. Silke Ospelkaus, Institut für Quantenoptik, Leibniz-Universität Hannover

Ultracold polar molecules (5. Juni 2012)

Tremendeous progress in the preparation and control of ultracold molecular gases promise to open exciting new research opportunities. Molecules rotate and vibrate and therefore offer many more quantum degrees of freedom than their atomic counterparts. Polar molecules interact via strong and long-range anisotropic interactions. These unique molecular properties provide largely unexplored novel opportunities. These range from the control of ultracold chemical reactions, precision measurements to strongly correlated dipolar quantum many-body systems. In this talk, I will take you on a tour through preparation and control of molecular quantum systems. We will see how ultracold all ground state molecular quantum systems can be efficiently created by means of a controlled chemical reaction at ultracold temperature; we will discuss how these molecular ensembles can be used to probe quantum chemistry and how chemical reactions can then be controlled and understood by simple laws of quantum mechanics. Finally, we will discuss prospects of these systems as novel dipolar quantum many-body systems.
 

Festkolloquium zum 100. Geburtstag von Prof. Dr. Erich Bagge (30. Mai 2012)

Programm:

14:00
  • Prof. Dr. Lutz Kipp - Begrüßung
  • Prof. Dr. Klaus Pinkau „Von der Auswertung der Kernspuremulsionen über die Gammastrahlen - Astronomie bis hin zur Energiegewinnung aus Kernfusion mit magnetischem Einschluss”
  • Prof. Dr. Joachim Trümper „Hochenergetische Teilchen und Röntgenstrahlung aus dem Kosmos”
  • Prof. Dr. Helmut Völcker „Die Entwicklung der Castor Behälter - Ein Beitrag der angewandten Kernphysik zur sicheren Entsorgung der Kernreaktoren”
16:00
  • Kaffeepause
16:30
  • Prof. Dr. Hans Georg Priesmeyer „GKSS, NS Otto Hahn und die Perspektiven”
  • Prof. Dr. Horst Willkomm „Der Aufbau und die Entwicklung des C14-Labors”
  • Horst Kunow „Von der Zugspitze zum Jupiter und um die Sonne – 50 Jahre Extraterrestrik in Kiel”
  • Prof. Dr. Robert Wimmer–Schweingruber „Mehr als durch die Glaskugel - Die Kieler Extraterrestrik heute und in der Zukunft”
Priv.-Doz. Dr. Axel Pelster, FU Berlin

Dipolar Bose-Einstein Condensates with Weak Disorder (15. Mai 2012)

The talk discusses several illustrative examples where ultracold dilute atomic gases provide important insights into condensed matter physics. We start with reviewing the properties of Bose-Einstein condensates (BECs) with the anisotropic and long-range dipole-dipole interaction. To this end we investigate the influence of quantum fluctuations upon the equilibrium configuration, the low-lying oscillation frequencies, and the time-of-flight dynamics. We find that both atomic magnetic and molecular electric dipolar BECs offer promising scenarios for detecting beyond mean-field effects. Furthermore, we report on recent progress in understanding the properties of ultracold bosonic atoms in potentials with quenched disorder. This notoriously difficult dirty boson problem is experimentally relevant for the miniaturization of BECs on chips and can also be studied by tailoring disorder potentials via laser speckle fields. Theoretically it is intriguing because of the competition of localization and interaction as well as of disorder and superfluidity. Finally, we combine both previous topics and consider the impact of weak disorder upon a polarized dipolar BEC at zero temperature. Surprisingly we find that disorder corrections of the superfluid density yield characteristic interaction-induced anisotropies which are not present in the absence of disorder.
 
Prof. Dr. Peter Beton, School of Physics and Astronomy - Nottingham

Order and Disorder in Two-dimensional Molecular Templates (24. April 2012)

The role of disorder in the formation of two-dimensional networks is currently attracting great interest and recent results on a supramolecular network which is stabilized by entropy and formed at a solid/liquid interface will be presented. These networks map directly onto a rhombus tiling of the plane and support a random tiling phase which has been studied widely by theorists over several decades but only recently realised experimentally. The networks are analyzed by treating them as projections of the (111) surface of a simple cubic crystal. The order within the arrays can then be characterized by from the height correlations of this virtual surface. It is also shown that topological defects are supported within this array. The choice of solvent is shown to be very important in the statistical properties of such arrays and phase transitions to ordered phases occur when the interaction between molecular tiles includes an asymmetric contribution which is comparable with the thermal energy kBT2. Growth of the networks, which are dynamically-arrested systems will also be consider. The trapping of guest species such as coronene and C60 in the random molecular rhombus network is also discussed. The presence of C60 leads to the growth of a second supramolecular layer stabilized by the guest molecule. This growth can be reversed through the introduction of coronene which displace the fullerene guest3. The role of disorder in the formation of covalently bound molecular networks will also be presented.