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aktualisiertes pdf - DPG-Tagungen

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detektor mit 80mm Durchmesser ab. Dieser Detektor, der für niedere<br />

Elektronenenergien entwickelt wurde/1/, ist mit einer multihitfähigen<br />

2d ortsempfindlichen Anode versehen, die die Elektronenlawinen hinter<br />

dem Channelplate-stack nachweist. Für hochenenergetische Elektronen<br />

nimmt die Nachweiseffizienz der Channelplates jedoch stark ab. Wir haben<br />

den nutzbaren Einsatzbereich des Detektors durch eine geeignet angepasste<br />

Channelplatekonfiguration erhöht und werden erste Ergebnisse<br />

vorstellen. 1 O. Jagutzki et al. NIM A477(2002)244-249<br />

A 15.22 Do 14:00 Schellingstr. 3<br />

A high-resolution detector for charge transfer experiments involving<br />

ultracold atoms — •Wenzel Salzmann, Helmut Rathgen,<br />

Roland Wester, and Matthias Weidemüller — Physikalisches<br />

Institut, Universität Freiburg, 79104 Freiburg<br />

We are setting up a new experiment to study ion-atom collisions using<br />

lasercooled atoms as an ultracold target. Projectile ions with energies of<br />

eV - keV pass through a magneto-optical trap where rubidium atoms are<br />

stored at temperatures below 100µK[1]. Target atoms which are ionised<br />

in the collision are momentum-analysed using Recoil-Ion-Momentum-<br />

Spectroscopy (RIMS)[2]. The low target temperatures correspond to very<br />

low momentum spreads of the rubidium atoms (δp < 0.01) which ensures<br />

a high resolution measurement of the recoil ion momentum components.<br />

We use this setup to examine several aspects of charge transfer reactions,<br />

in particular dissociative charge transfer to diatomic molecular ions at<br />

eV-keV energies. By using a defined projectile beam one can extract<br />

detailed information from the recoiled ion about the internal electronic<br />

state of the neutral molecule after the collision. The dissociated states<br />

are analysed by detecting the neutral fragments and their kinetic energy.<br />

In order to prepare the ions in a defined state they are stored in a linear<br />

electrostatic ion trap at keV energies or in a Rf-trap at eV energies. The<br />

status of the experiment is presented.<br />

[1] M.v.d. Poel et al., Phys. Rev. Lett. 87, 12, 3202(2001).<br />

[2] J.Ullrich et al., J. Phys. B,30, (1997), 2917-2974.<br />

A 15.23 Do 14:00 Schellingstr. 3<br />

Fabrication of Atom Chips and their electrical properties —<br />

•Sönke Groth 1,2 , Peter Krüger 1 , Stephan Wildermuth 1 , Diana<br />

Mahalu 2 , Israel Bar-Joseph 2 , and Jörg Schmeidmayer 1 —<br />

1 Physikalisches Institut, Heidelberg, Germany — 2 Weizmann Institute of<br />

Science, Rehovot, Israel<br />

Atom Chips are used to trap neutral atoms and cool them by laser<br />

and evaporative cooling even to BEC. The advantages of atom chips are<br />

smooth surfaces for non scattered laser reflection, high current densities<br />

up to 10 7 A/cm 2 , micro shaped wires for exactly defined potentials, wire<br />

thickness from nm to µm scale and serial production.<br />

A high quality preparation process based on nanofabrication lithography<br />

capable of structures ∼ 1 µm is shown, which achieves the mentioned<br />

criteria. Electrical properties of these atom chips are investigated<br />

for measurements of wires with different aspect ratios on several substrates.<br />

The heat conductivity of the substrate is of importance for the<br />

lifetime of the wire. The technology aspects for miniaturised quantum<br />

manipulation atom optics are discussed.<br />

A 15.24 Do 14:00 Schellingstr. 3<br />

Trapping of heavy alkaline earth elements — •Umakanth<br />

Dammalapati, Gerald Ebberink, Klaus Jungmann, and Lorenz<br />

Willmann — Kernfysisch Versneller Instituut, Zernikelaan 25, 9747<br />

AA Groningen, The Netherlands<br />

We are working toward a search for a permanent electric dipole moment<br />

(edm) of a fundamental particle. An edm, which violates time reversal<br />

symmetry (T) as well as the combination of charge conjugation symmetry<br />

(C) and parity (P), is an unambiguous signal for physics beyond the standard<br />

model. Some short lived radioactive elements and the techniques for<br />

trapping and cooling of atoms offer new possibilities for edm searches. At<br />

the KVI a facility for producing short lived radioactive isotopes (TRIµP)<br />

is being set up. Here, the heavy alkaline earth element radium will be<br />

produced. Radium promises to have a high sensitivity for edm searches<br />

because of a large enhancement due to the unique level structure, which<br />

exhibits almost degenerate P and metastable D states [1]. In order to<br />

learn and develop the spectroscopic techniques and trapping tool, we are<br />

working in parallel with barium, which has a level scheme very similar<br />

to radium. As a first step we will measure the lifetime of the metastable<br />

D-states as well as their hyperfine structure splitting. Once radium is<br />

available at KVI we will use our experience to do this spectroscopy with<br />

radium. We report on the status of the experiment and prospects for the<br />

26<br />

future.<br />

[1] V.A. Dzuba, V.V. Flambaum, and J.S.M. Ginges, Phys. Rev. A 61,<br />

062509 (2000); V.V. Flambaum, Phys. Rev. A 60, R2611, (1999).<br />

A 15.25 Do 14:00 Schellingstr. 3<br />

Fano’s model in an external periodic perturbation: Exact analytical<br />

solution — •N.B. Sangouard, R.G. Unanyan, L. Plimak,<br />

and M Fleischhauer — Fachbereich Physik, Universität Kaiserslautern,<br />

67653, Kaiserslautern, Germany<br />

Decay of a discrete state into continuum when the amplitude of the<br />

former is inverted periodically is investigated. A decaying ”Floquetresonance”<br />

solution of the Schrödinger equation valid for times large<br />

compared to the inversion period is identified. The decay rate, i.e., the<br />

imaginary part of the quasienergy of the ”Floquet resonance,” can be<br />

controlled by changing the period of the perturbation. Interestingly, the<br />

periodic inversions result in boundedness of the decay rate which stays finite<br />

for an arbitrarily strong coupling between the discrete state and continuum.<br />

This can have interesting applications in quantum computing,<br />

interferometry, and coherent control of reaction optical memory storage,<br />

dynamics.<br />

A 15.26 Do 14:00 Schellingstr. 3<br />

Abbremsung von SO2 mit zeitabhängigen elektrischen Feldern<br />

— •Sebastian Jung, Christian Lisdat und Eberhard Tiemann<br />

— Institut für Quantenoptik, Universität Hannover, Welfengarten 1,<br />

30167 Hannover, Germany<br />

Da sich die für Atome sehr effiziente Methode der Laserkühlung nicht<br />

allgemein auf Moleküle übertragen läßt, sind andere Ansätze zu deren<br />

Erzeugung notwendig. Experimentell realisiert wurden die Bildung von<br />

Molekülen aus kalten Atomen, Puffergaskühlung und die Abbremsung<br />

von polaren Molekülen in Teilchenstrahlen mit elektrischen Feldern.<br />

In unserem Experiment sollen SO2-Moleküle mit der zuletzt genannten<br />

Technik gebremst und gefangen werden. SO2 stellt aufgrund seiner großen<br />

Masse eine Herausforderung dar, bietet aber die Möglichkeit, Photodissoziation<br />

zur Erzeugung von kaltem O und SO zu nutzen. Beide Fragmente<br />

entstehen in Triplett-Zuständen, die magnetisch gefangen werden<br />

können. Photodissoziation in externen Feldern erlaubt die Untersuchung<br />

von Feshbachresonanzen.<br />

Der Stand der Experimente in Hinblick auf die Erzeugung eines kalten<br />

Strahls wird dargestellt und Simulationen für elektrostatische Linsen und<br />

den Abbremser beschrieben.<br />

A 15.27 Do 14:00 Schellingstr. 3<br />

Quasi-one-dimensional Bose and Femi gases under external confinement<br />

— •Doerte Blume 1 , Grigori Astrakharchik 2 , Stefano<br />

Giorgini 2 , and Brian Granger 3 — 1 Department of Physics,<br />

Washington State University, Pullman, Washington 99164-2814, USA —<br />

2 Dipartimento di Fisica, Universita di Trento and BEC-INFM, I-38050,<br />

Povo, Italy — 3 Department of Physics, Santa Clara University, California<br />

95053, USA<br />

Bose gases confined in highly-elongated harmonic traps are investigated<br />

over a wide range of interaction strengths using quantum Monte<br />

Carlo techniques. We find that the properties of these gases are well reproduced<br />

by a 1d model Hamiltonian with contact interactions. We point<br />

out the existence of a unitary regime, where the properties of the quasi-<br />

1d Bose gas become independent of the actual value of the 3d scattering<br />

length. In this unitary regime, the energy of the system is well described<br />

by a hard rod equation of state. The stability of quasi-1d Boses gases with<br />

positive and negative 3d scattering length is discussed. We contrast the<br />

behaviors of quasi-1d Bose gases with those of quasi-1d two-component<br />

Fermi gases and quasi-1d spin-polarized Fermi gases.<br />

A 15.28 Do 14:00 Schellingstr. 3<br />

Experiment for the preparation of an ultracold dense gas<br />

of Rydberg atoms — •Markus Reetz-Lamour 1 , Kilian<br />

Singer 1 , Thomas Amthor 1 , Simon Fölling 2 , and Matthias<br />

Weidemüller 1 — 1 Physikalisches Institut, Universität Freiburg, 79104<br />

Freiburg — 2 Johannes-Gutenberg-Universität, 55128 Mainz<br />

We report on an experiment, which is designed to investigate manybody<br />

effects in a dense gas of cold Rydberg atoms. Our setup consists<br />

of a very compact vacuum system where 10 8 87 Rb atoms at a density<br />

of 10 10 cm −3 are confined in a magneto-optical trap. The magnetic field<br />

is provided by coils inside the vacuum, the atoms are loaded from dispensers.<br />

After trapping and cooling down to 1µK with degenerate 3D<br />

Raman sideband cooling [1] the atoms are excited via a 2-photon transi-

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