Quantum gas of deeply bound ground state molecules

J.G. Danzl, Elmar Haller, M. Gustavsson, M.J. Mark, R. Hart, N. Bouloufa, O. Dulieu, H. Ritsch, H.-C. Nägerl

Research output: Contribution to journalArticlepeer-review

313 Citations (Scopus)


Molecular cooling techniques face the hurdle of dissipating translational as well as internal energy in the presence of a rich electronic, vibrational, and rotational energy spectrum. In our experiment, we create a translationally ultracold, dense quantum gas of molecules bound by more than 1000 wave numbers in the electronic ground state. Specifically, we stimulate with 80% efficiency, a two- photon transfer of molecules associated on a Feshbach resonance from a Bose- Einstein condensate of cesium atoms. In the process, the initial loose, long- range electrostatic bond of the Feshbach molecule is coherently transformed into a tight chemical bond. We demonstrate coherence of the transfer in a Ramsey- type experiment and show that the molecular sample is not heated during the transfer. Our results show that the preparation of a quantum gas of molecules in specific rovibrational states is possible and that the creation of a Bose- Einstein condensate of molecules in their rovibronic ground state is within reach.
Original languageEnglish
Pages (from-to)1062-1066
Number of pages5
Issue number5892
Publication statusPublished - 22 Aug 2008


  • molecular cooling
  • quantum gas
  • Bose-Einstein condensate
  • cesium atoms


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