Berlin 2014 – scientific programme

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MO: Fachverband Molekülphysik

MO 1: Cold Molecules 1

MO 1.4: Talk

Monday, March 17, 2014, 11:30–11:45, BEBEL HS213

Optimal Control of Vibrational Cooling — •Daniel Reich and Christiane Koch — Theoretische Physik, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel

Laser cooling of a molecule's internal degrees of freedom employing broadband optical pumping involves a timescale separation between laser excitation and spontaneous emission. Current approaches fail if the Franck-Condon map governing the optical transitions is preferential to heating rather than cooling. We show that by using optimal control theory to derive shaped pulses for the optical pumping step this issue can be circumvented entirely. To achieve this we have designed two different cooling schemes and corresponding optimisation functionals [1]. The optimised pulses drive population into those excited state levels that have the largest spontaneous emission rates to the target state while accumulating population in the ground state and keeping the cooling cycle loss-free. Our optimisation functionals are also applicable to the laser cooling of other degrees of freedom provided the cooling cycle consists of coherent excitation and dissipative deexcitation steps whose timescales are separated.

[1] D.M. Reich and C.P. Koch, New J. Phys. (to be published)