Atomic anions are generally not amenable to optical spectroscopy because they are loosely bound systems and rarely have bound excited states. Until now, there are only very few negative ion with a bound–bound electronic transition. These electric-dipole transitions may provides unique insight into the structure of atomic anions.

In addition, it may enable the preparation of ultracold ensembles of negative ions. Currently available cooling techniques for negatively charged particles allow cooling only to the temperature of the surrounding cryogenic environment, typically at 4 K if the apparatus itself is cooled with liquid helium. At these temperatures, the achievable precision of spectroscopic measurements is often limited by inhomogeneous broadening due to thermal motion. Laser excitation of the electric-dipole transition in anions could be used to laser-cool them to microkelvin temperatures.

If demonstrated to be successful, the technique would allow the cooling of any species of negatively charged particles – from subatomic particles to molecular anions – to ultracold temperatures by sympathetic cooling. We have been investigating the bound–bound electric-dipole transition in negative osmium by high- resolution laser spectroscopy with a view to using it for the first laser cooling of negative ions. The principle of the method, its potential applications, as well as experimental results will be presented.<:div>

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Contacts séminaires :

• Jean-Pierre GALAUP
• Laurence PRUVOST

tel : 01 69 35 21 01

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