SIGNIFICANT EVENTS - SCIENCE EVENTS
08/20/04
Ketterle Group Presents Invited Talks on Molecular BEC
Molecular condensates could lead to a host of new scientific explorations, including studying quantum
gases with anisotropic interactions, tests of fundamental symmetries such as the search for a
permanent electric dipole moment, the study of rotational and vibrational energy transfer processes,
and coherent chemistry, where reactants and products are in coherent quantum superposition states.
Recently the Ketterle group at MIT has been invited to present talks describing their studies of
the transition of 6Li atoms into molecular BEC states.
When a spin mixture of fermionic 6Li atoms is evaporatively cooled in an optical dipole trap near
a Feshbach resonance, the atomic gas is converted into diatomic molecules. Below 600 nK, a
Bose-Einstein condensate of up to 900,000 molecules was identified by the sudden onset of a bimodal
density distribution (see photo). This BEC realizes the limit of tightly-bound fermion pairs in
the crossover between BCS superfluidity and the BEC state.
These studies were reported at the March Meeting of the American Physical Society in Montreal
as "Observation of Bose-Einstein Condensation of Molecules" and again at the Conference on
Quantum Gases, Institute for Theoretical Physics (ITP) Santa Barbara, as "Condensation of pairs
of fermionic lithium atoms below and above a Feshbach resonance."
Observation of Bose-Einstein condensation in a cold molecular gas. Shown are three single-shot
absorption images after 6 milliseconds of ballistic expansion for progressively lower temperatures
(left to right). The appearance of dark spots (the bimodal density distribution) marks the onset of
BEC. The field of view for each image is 1.4 X 1.4 mm2.
