Berlin 2001 – wissenschaftliches Programm
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AMPD: EPS AMPD
AMPD 8: Sitzung 8
AMPD 8.3: Vortrag
Donnerstag, 5. April 2001, 11:30–11:55, H104
New results on cold Rb2* molecular formation — •C. Gabbanini1, A. Fioretti1, M. Mazzoni2, and G. Smirne1 — 1Istituto di Fisica Atomica e Molecolare del C.N.R., Via Alfieri 1, 56010 Ghezzano, Pisa, Italy — 2Istituto di Elettronica Quantistica del C.N.R., Via Panciatichi 56, 50127 Firenze, Italy
The extension of laser cooling techniques from atoms to molecules is very difficult because of the lack of closed two–level transitions for performing efficient cooling. However the photoassociation process of laser-cooled atoms, where colliding atom pairs get bound after the absorption of a photon, can produce translationally cold molecules in the excited state. In some particular cases these excited dimers can spontaneously decay with a significant probability into ground state molecules that remain translationally cold. Here recent studies on the formation of translationally cold rubidium molecules will be presented. Ultracold molecules are produced starting from laser–cooled Rb atoms inside a magneto–optical trap [1]. The cold dimers are mainly formed in the a3Σu+ triplet ground state with a translational temperature of about 90 µK. The neutral dimers are converted into molecular ions through two–photon ionization by a pulsed dye laser; the molecular ions are detected after time–of–flight selection. The role of the processes contributing to the molecular formation, that are photoassociation and three–body recombination, will be discussed. In particular the formation of cold molecules through photoassociation of the 0g− (5S+5P3/2*) state has been studied in detail [2]. As already observed for cesium [3], this attractive long-range electronic state has favorable Franck–Condon factors for spontaneous decay into ground state molecules. The final distribution of cold molecules into the vibrational levels of the ground triplet state has also been determined. Finally new and future experimental directions will be discussed.
[1] C. Gabbanini, A. Fioretti, A. Lucchesini, S. Gozzini, and M. Mazzoni, Phys. Rev. Lett. 84, 2814 (2000).
[2] A. Fioretti, D. Comparat, A. Crubellier, O. Dulieu, F. Masnou–Seeuws, and P. Pillet, Phys. Rev. Lett. 80, 4402 (1998).
[3] A. Fioretti et al., sub. Eur. Phys. J. D.