Hannover 2010 – scientific programme

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MO: Fachverband Molekülphysik

MO 24: Poster: Quantum Control

MO 24.9: Poster

Thursday, March 11, 2010, 16:00–18:30, Lichthof

State selection in rotational wave packets by tuning from nonadiabatic to adiabatic interaction — •Nina Owschimikow¹, Burkhard Schmidt², and Nikolaus Schwentner¹ — ¹Institut für Experimentalphysik, Freie Universität Berlin — ²Institut für Mathematik, Freie Universität Berlin

Non-adiabatically excited rotational wave packets display periodically recurring revivals of alignment after the termination of the excitation pulse. The amplitude of these oscillations decreases as the adiabatic limit is approached with increasing pulse duration. We show by numerical simulations for the nitrogen-molecule that this can be described as a convolution of pulse envelope and sinusoidal rotational response and it results in a unique dependence for all J quantum states on the ratio of pulse duration to rotational period.

In a thermal ensemble of molecules, a wide distribution of rotational levels is populated, with the crossover from the non-adiabatic to the adiabatic limit varying according to rotational frequency. Increasing the excitation pulse duration restricts the coherent post-pulse response to the cold part of the thermal distribution, thus creating a "cool" wave packet in a thermal bath. A pair of pump and dump pulses with the duration of the dump pulse tuned to interact non-adiabatically only with the rotationally "cool" molecules additionally serves to limit the coherence to the hot part of the distribution, thus allowing for state selectivity in spite of the non-resonant excitation mechanism.