[seminar] Kolokvij IRB, Pillet

[Hrvoje Buljan]

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Srdačan pozdrav
Hrvoje Buljan

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Institutski kolokviju IRBa
u srijedu 10. 12 u 16 sati u predavaonici III krila

     Cold molecules: formation with cold atoms and laser cooling

                    Pierre Pillet
              Laboratoire Aime Cotton
               CNRS, Univ Paris-Sud

       New perspectives in the field of cold molecules have
been opened in 1998 with the demonstration producing cold samples
of ground-state of dimers of cesium in the microkelvin temperature
range, via photoassociation of cold cesium atoms. This result has
been quickly followed by the elaboration of various methods to
prepare cold molecules in the kelvin or millikevin temperature
range, by starting with molecules, such as cryogenically cooled
buffer gas, slow down of supersonic beam, velocity filtering of
an effusive beam???  Until now, cold molecules in the micro-range
can only been achieved starting with cold atoms. The methods of
producing cold molecules from cold atoms (via photoassociation
in cold thermal gases or through magneto-association in quantum
gases as Bose-Einstein condensates), however, lead to the
production of vibrational excited molecules. New progresses have
been recently obtained by several groups with different approaches.
The vibrational cooling through optical pumping using a shaped
broadband femtosecond laser has been demonstrated for Cs??? molecules.
The molecules initially formed via photoassociation of cold cesium
atoms are in several vibrational levels, v, of the singlet ground
state. The broadband femtosecond laser can electronically excite
the molecules, leading via a few absorption - spontaneous emission
cycles, to a redistribution of the vibrational population in the
ground state. By removing the laser frequencies corresponding to
the excitation of the v=0 level, we realize a dark state for the
so-shaped femtosecond laser, yielding with the successive laser
pulses to an accumulation of the molecules in the v=0 level.
The method opens novel perspectives for vibrational and rotational
cooling, and for the laser manipulation of molecules.
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