Hannover 2010 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 20: Ultra Cold Atoms, Ions and BEC I (with A)

Q 20.1: Invited Talk

Tuesday, March 9, 2010, 14:00–14:30, F 303

Probing weakly bound molecules with nonresonant light — •Mikhail Lemeshko and Bretislav Friedrich — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany

We show that weakly-bound molecules, such as those created via Feshbach resonances or photoassociation of ultracold atoms, can be accurately probed by "shaking" in a pulsed nonresonant laser field. The technique relies on the ability to impart a tunable value of angular momentum to the weakly bound molecule such that the centrifugal term concomitant with it expels the molecule's vibrational level from the potential and thus causes the molecule to dissociate. The laser intensity needed to impart a preordained value of the angular momentum varies characteristically with the internuclear distance. It is this characteristic dependence that can be used to map out the probability density of the vibrational state from which the molecule was forced to dissociate. A highly accurate long-range molecular potential can then be retrieved by inverting the vibrational probability density. This route to an accurate potential, independent of spectroscopy or scattering, complements what can be learned from either. We illustrate the technique's machinery by examining Feshbach molecules of acute interest, Rb2 and KRb. In addition, we discuss the possibilities to control the molecular size, the positions of Feshbach resonances, and the photoassociation probability using cw laser fields, and note that the laser field of an optical dipole trap may dissociate some of the most weakly bound molecules via the "shaking" mechanism.