Hannover 2013 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 13: Quantum Chemistry and Molecular Dynamics II
MO 13.8: Vortrag
Dienstag, 19. März 2013, 15:45–16:00, F 107
Fluctuations in Laser-Aligned Molecules — •Yi-Jen Chen1,2, Stefan Pabst1,2, Zheng Li1,2, Oriol Vendrell1, and Robin Santra1,2 — 1Center for Free-Electron Laser Science (CFEL), DESY, Hamburg, Germany — 2Department of Physics, University of Hamburg, Hamburg, Germany
Aligning molecules is essential for probing and controlling various kinds of physical processes and chemical reactions. Therefore, the field of laser-aligned molecules has been of much and growing research interest in the past decade. In the present study, we address the following fundamental question: To what degree is it possible to describe laser-induced molecular alignment using classical mechanics? It is known that the appearance of periodic revivals in impulsive alignment is a purely quantum-mechanical phenomenon. However, the alignment dynamics during and right after the laser pulse has been shown to have strongly classical features. The observable generally used for describing molecular alignment is O=cos2θ, where θ is the angle between the figure axis of the molecule and the direction of the laser polarization. Conventionally, the degree of alignment is characterized by the expectation value ⟨ O ⟩. Here, we investigate fluctuations in molecular alignment by calculating the uncertainty Δ O. Specifically, we computationally investigate an ensemble of laser-aligned bromine molecules. The time evolution of the ensemble is numerically determined by quantum as well as classical simulations under various temperatures and laser-pulse parameters. By comparing the quantum to the classical results, we assess the role of quantum fluctuations in molecular alignment.