Third Microsymposium of the "International Scholarship Program for Graduate Studies in Faculty of Chemistry, University of Warsaw - From simple molecules to nanostructured and bioactive materials" October 6 - 8th, 2011, Palace in Łochów, Poland
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Thursday Oct. 6th 12:45 - 13:15 - Michał Tomza Controlling the multi-photon photoassociation of ultracold molecules with laser pulses We investigate the possibility of coherently forming deeply bound ultracold Rb2 molecules using multiphoton transitions driven by shaped femtosecond laser pulses. In multi-photon processes a broadband laser can drive a narrow transition due to optical interference. Furthermore modified selection rules apply to multiphoton transitions compared to single-photon ones allowing for novel pathways of molecule formation. We determined the required electronic structure of the rubidium molecule using state-of-the-art ab initio techniques calculating potential energy curves, electric transition dipole moments, nonadiabatic radial and angular coupling matrix elements, and spin-orbit coupling matrix elements for all singlet and triplet states below 26000 cm-1. We employ the electronic structure data to investigate the nuclear dynamics of multi-photon transitions with laser pulses shaped using coherent and optimal control. Starting from an atom pair colliding in the a3Σu+ lowest triplet state, we propose three-photon photoassociation with pulses shaped such as to suppress purely atomic transitions. Photoassociating into states with partial ion-pair character is expected to enhance the total efficiency of proposed process. Subsequent stabilization using a two-photon transition driven by optimally shaped pulses should allow for the efficient production of rubidium molecules in the 1Σg+ ground electronic state. Photoassociation represents a basic example for coherent control of a binary reaction 
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