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MO: Fachverband Molekülphysik
MO 7: Quantenkontrolle
MO 7.1: Talk
Tuesday, March 11, 2008, 14:00–14:15, 3F
Coherent control of excited state dynamics in a Pump Degenerate-Four-Wave-Mixing (Pump-DFWM) experiment — •Jürgen Hauer1, Tiago Buckup1, Judith Voll2, Regina Vivie-Riedle2, and Marcus Motzkus1 — 1Physikalische Chemie, Philipps-Universität Marburg, D-35043 Marburg, Germany — 2Department Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
Coherent control is generally known as a method for aim directed manipulation of the interaction between light and matter. In literature, there are numerous examples where coherent control favours certain target quantum states while suppressing unwanted ones. We further the concept of modulated light-matter interaction to a novel kind of spectroscopy termed Quantum Control Spectroscopy (QCS), where molecular features hidden from Fourier-limited excitation are brought to light by phase-modulated pulses. As an example, we investigate β-carotene with Pump-Degenerate Four Wave Mixing (Pump-DFWM). Scanning the relative phase between the sub-pulses of a pulse sequence reveals a low-frequency coupling mode near 200 cm−1 between the first two exited states S2 and S1. Besides this novel feature, we also show that differently spaced multipulses affect the ultrafast lifetime of the initially populated S2-state. We substantiate our findings by an in-depth theoretical analysis based on wavepacket dynamics, exhibiting a quantitative agreement between theory and experiment. In a final set of investigations, we explore the degree to which vibrational cooling can be coherently controlled or averted by phase modulation.