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MO: Molekülphysik

MO 51: Molecular Quantum Control

MO 51.5: Talk

Thursday, March 16, 2006, 11:40–11:55, H12

Selective Spectral Filtering of Molecular Modes in Solution Phase Using Optimal Control in Four-Wave-Mixing Spectroscopy — •J. Konradi, A.V. Scaria, A.K. Singh, and A. Materny — International University Bremen, Germany

Due to their many degrees of freedom, femtosecond time-resolved four-wave mixing (FWM) techniques like CARS (coherent anti-Stokes Raman scattering) give access to different aspects of ultrafast dynamics. While the temporal resolution is high in fs spectroscopy, the resulting signals only have a poor spectral resolution. Coherent control techniques using tailored laser pulses allow for a manipulation of molecular multi-mode dynamics. Recently, we have demonstrated, that by shaping the pulses using a learning-loop optimal control scheme, in the FWM-spectrum vibrational modes can be selectively enhanced or suppressed [1]. Here, the ratio of the signal intensities for different lines in the nonlinear Raman spectrum served as feedback signal for an evolutionary algorithm. In our contribution we will present our latest results on frequency selective femtosecond spectroscopy. We have applied the optimal control technique in combination with electronically resonant as well as nonresonant four-wave mixing processes. We will demonstrate that in both cases the spectral resolution can be improved considerably by keeping the temporal resolution high. In order to gain information about the fundamental mechanism behind the spectrum control, an analysis of the experimental data has been performed, which will be discussed in detail.

[1] J. Konradi, A. K. Singh, A. Materny, Phys. Chem. Chem. Phys., 7, 3574, (2005)