Veranstaltungskalender

Atomphysik-Seminar

• Mittwoch, 08. Februar 2012   11.00 Uhr -- Vorraum Atomphysik, Südbau, II. Stock
  Martin Breitenfeldt, CERN, Genf
  "First high-quality data with 35Ar: The search for scalar weak currents with WITCH"
  

  Low energy precision experiments for the search of exotic components in the weak interaction are complementary to the high energy experiments at the colliders dedicated to discover new particles. In the case of the WITCH experiment the beta neutrino angular correlation coefficient (a) in nuclear beta decay is studied. A deviation from the distribution as predicted by the standard model will reveal the exotic interactions. For the study of the weak interaction WITCH combines a Penning trap arrangement to provide a scattering free source of beta-decaying nuclides with a MAC-E filter setup to analyze the recoil energy distribution. In the online experiments of last year it was finally possible to acquire the first sets of data, meaning recoil spectra of 35Ar ions. The first experiment resulted in a recoil spectrum with about 5000 events recorded. This first spectrum has been analyzed with the help of simulation programs developed in the collaboration and under consideration of the charge state distribution of the daughter nuclei, which has been determined at LPCtrap/GANIL. The result is a value of a = 1.12(33) which is compatible with the literature value for 35Ar. During the second online experiment in 2011 several more recoil spectra each with higher statistics were acquired, which were obtained using various spectrometer voltage sequences. These data are currently under analysis. A first estimation points for a statistical uncertainty on the value of a in the order of 2%. This will allow the investigation of systematic effects in the data as studied before by numerical simulations.
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• Donnerstag, 16. Februar 2012   15.00 Uhr -- Vorraum Atomphysik, Südbau, II. Stock
  Andrey Surzhykov, University of Heidelberg and Atomic Physics Division of GSI
  "Relativistic quantum theory of few–electron systems in strong fields: Atomic physics at high–Z"
  

  Highly-charged ions provide today an ideal ``playground’’ for studying few-electron systems exposed to extremely strong electromagnetic fields produced by heavy nuclei. In such a strong-field regime, the relativistic, many-body and quantum electrodynamics (QED) effects become of paramount importance and may significantly affect not only the shell structure but also the collision dynamics of the few-electron heavy species. In order to probe the properties and behaviour of high-Z ions and, hence, to improve our understanding of atomic physics under such extreme conditions a broad research program is currently being undertaken at GSI and will be further expanded at the future Facility for Antiproton and Ion Research (FAIR). The ultimate success of this program will of course require a deep theoretical understanding of the underlying physics. In this contribution therefore, a review is presented of recent theoretical activities in the field of high-Z atomic physics. Special emphasis will be placed on the studies of fundamental symmetries and interactions in which highly-charged heavy ions can play a decisive role. Moreover, the advances in the non-perturbative analysis of basic atomic processes accompanying ion-ion collisions will be presented. Here we will focus not only on the ultra–relativistic collisions but also especially on the low-energy regime for which the quasi–molecular effects may become of critical importance. Finally, the studies on the linear as well as non-linear photon-matter interactions in the extreme relativistic regime will be briefly discussed.
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