34
nanotimes
10-01 :: January 2010
News in Brief
Ultracold Chemistry //
First Direct Observation of Exchange Process in Quantum Gas
T
he research team of Rudolf Grimm from the
Institute for Experimental Physics at the Uni-
versity of Innsbruck, Austria, and the Institute for
Quantum Optics and Quantum Information of the
Austrian Academy of Sciences, has succeeded in
directly observing chemical exchange processes
in an ultracold sample of cesium atoms and Fesh-
bach molecules. For the first time, great progresses
made in the field of ultracold atomic and molecular Image: When a molecule (two blue spheres) collides with
gases have facilitated the realization of elementary
an atom (single red sphere), an atom can be exchanged.
chemical processes in a fully controlled way, where
A new molecule is produced (red and blue spheres) and
an atom (single blue sphere) is released. In the experi-
all particles can be prepared in a specifically defined
ment performed in Innsbruck this process is observed at
quantum state. “Our experiment showed that it is
temperatures of less than one millionth above the abso-
possible to control exchange processes involving
lute zero. The exchange is completely determined by the
ultracold molecules“, Grimm says excitedly.
quantum nature of the matter and can be controlled by a
magnetic field. © IQOQI
The scientists optically trap cesium atoms and cool
them dramatically. A Feshbach association results in
an ultracold particle cloud consisting of about 4,000 energy produced in this exoergic process is very low,
molecules and 30,000 atoms, where a part of the the reaction products remain in the trap,“ explains
atoms are arranged in dimers. By applying a micro- Rudolf Grimm. “Thus, we were able to directly ob-
wave pulse, the atoms are transferred into another serve the chemical process for the first time ever.“
quantum state without the molecules being modified.
After preparing this mixture of molecules (A+A) and
atoms (B), the experimental physicists apply a certain S. Knoop, F. Ferlaino, M. Berninger, M. Mark, H.-C.
magnetic field, which allows them to fully control Nägerl, R. Grimm, J. P. D‘Incao, B. D. Esry: Magnetically
the binding energy of the molecules. The collision Controlled Exchange Process in an Ultracold Atom-Dimer
of the molecules and atoms results in an exchange Mixture, In: Physical Review Letters, 104, 053201 (2010)
process when a certain threshold of binding energy is

http://dx.doi.org/10.1103/PhysRevLett.104.053201
reached. The original molecules decay to atoms (A)
and new molecules are produced (A+B). “Since the

http://www.uibk.ac.at/exphys/ultracold/