Darmstadt 2008 – scientific programme

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A: Fachverband Atomphysik

A 26: Posters: BECs, ultracold gases and plasmas

A 26.1: Poster

Thursday, March 13, 2008, 16:30–18:30, Poster C3

Cold collisions of K atoms studied by precision spectroscopy — Stephan Falke^1,2, Matthias Riedmann¹, Jan Friebe¹, Horst Knöckel¹, Eberhard Tiemann¹, and •Christian Lisdat^1,3 — ¹Institut für Quantenoptik, Leibniz Universität Hannover — ²Department of Physics, Yale University, New Haven, U.S.A. — ³Physikalisch-Technische Bundesanstalt Braunschweig

The interaction in ultracold thermal and quantum degenerate atomic clouds are dominated by binary collisions. Precisely these interactions make ultracold atoms the interesting field of research they are, since they determine BEC properties, produce Feshbach resonances, or allow forming molecules. All these points are closely related to the interaction potential of two colliding atoms. We report our laser-spectroscopic investigation of the least bound levels in the ground state X ¹Σ_g⁺ of ³⁹K₂ undertaken on a molecular beam [1]. We measured in a two-laser lambda scheme energy differences of ground state levels in the order of 1 250 cm⁻¹ with a precision better than 5 MHz applying a femtosecond frequency comb and iodine lines for frequency calibration. Precise models of the interaction potentials allow for an accurate description of cold collisions, e.g., Feshbach resonance positions. In a further step of the experiment we will test the precision of the mass-scaling to other isotope combinations based on the Born-Oppenheimer approximation using the isotopomere ³⁹K⁴¹K, which is sufficiently abundant for observation in a molecular beam based on a natural potassium [1].

[1] J. Chem. Phys. 125, 224303 (2006), Phys. Rev. A 76, 012724 (2006).