Quantum Wavepacket Dynamics in Molecular and Trapped Ion Systems
Wednesday 30 April 2008
to 14:30 at
Dong Wang (Department of Physics, Stockholm University)
The motions of a wavepacket in the two coupled potentials studied in this thesis can be classified into either bistable or astable motion according to the wavepacket interference at the curve crossing.
Bistable motion, in wich the wavepacket performs a coupled oscillation but remains in the same adiabatic and diabatic state, can exist both in bound-bound systems and bound-unbound ones with long time stability.
Astable motion, in which the wavepacket at the curve crossing switches between the adiabatic and diabatic states and thus alternates between the two possible turning points in the unforked part of the motion, can only exist in bound-bound systems on a limited time scale.
The motion of a wavepacket under bistable interference conditions exhibits all of the features expected if the wavepacket moved in a single anharmonic potential. The revival time can be predicted from the revival times in the corresponding diabatic and adiabatic potentials. The phenomenon was observed not only in model molecular systems but also in the system of the harmonically trapped ion pumped by an external laser field with standing wave spatial profile.
In order to study the bias effect of the detector on pump-probe rotational anisotropy measurements, in a specific direction the fluorescence polarization effect was removed by measuring the rovibrational wavepacket with the help of properly oriented polarizer placed in front of the detector. Our results show clearly the necessity to take polarization effects into account in ultrafast pump-probe rotational anisotropy measurements.