Schedule Mar 15, 2013
Optimized Production of Ultracold Ground-state Molecules: Stabilization Employing Potentials with Ion-pair Character and Strong Spin-orbit Coupling
Michal Tomza (Univ. of Warsaw)

Michal Tomza, Michael H. Goerz, Monika Musial, Robert Moszynski, Christiane P. Koch 

Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland

Theoretische Physik, Universitat Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany

We discuss the production of ultracold Rb2 molecules in their electronic ground state by multiphoton photoassociation employing electronically excited states with ion-pair character and strong spin-orbit interaction [1]. In multi-photon processes a broadband laser can drive a narrow transition due to optical interference [2]. Furthermore modified selection rules apply to multiphoton transitionscompared to single-photon ones allowing for novel pathways of molecule formation. We have determined the required electronic structure of the rubidium molecule using state-of-the-art ab initio techniques and have employed it to investigate the nuclear dynamics of multi-photon transitions with shaped femtosecond laser pulses. A short photoassociation laser pulse drives a non-resonant three-photon transition for alkali atoms colliding in their lowest triplet state. The excited state wave packet is transferred to the ground electronic state by a second laser pulse, driving a resonant two-photon transition. The transition matrix elements governing the stabilization step are compared to the efficiency of population transfer using transform-limited and linearly chirped laser pulses. Finally, we have employed optimal control theory to find the most efficient stabilization pathways. 

[1] M. Tomza et al., Phys. Rev. A 86, 043424 (2012).

[2] D. Meshulach, Y. Silberberg, Nature 396, 239 (1998).

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