Berlin 2005 – scientific programme

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MO: Molekülphysik

MO 35: Quantum Control II

MO 35.5: Talk

Monday, March 7, 2005, 17:30–17:45, HU 2091

Molecule-Specific Spectroscopy in Frequency and Time Domain Using Optimal Control of Femtosecond Laser Pulses — •Ajay K. Singh, Jakow Konradi, and Arnulf Materny — International University Bremen, School of Engineering and Science, Campus Ring 1, 28759 Bremen (e-mail: a.materny@iu-bremen.de)

For several applications, like microscopic imaging of biological samples, it is of utmost importance to filter out contributions of certain components. Different techniques are used for this purpose. Laser spectroscopy enables one to identify specific substances in a complex sample or a mixture of different chemicals. Recently, we were able to demonstrate that by controlling the phase shape (“chirp”) of a femtosecond laser pulse in a nonlinear four-wave mixing process, vibrational modes of the molecules could be selectively enhanced in the spectrum. In our contribution we will present results of femtosecond CARS (Coherent anti-Stokes Raman Scattering) experiments on systems consisting of different chemical compounds. We have applied a computer-controlled pulse shaper to optimize the phase shape of one of the interacting laser pulses such that contributions of one component are selectively enhanced over the spectral lines of the rest in the CARS spectrum. The optimization process is guided by a learning evolutionary algorithm. In our presentation we will discuss possible mechanisms behind the selective filtering of molecule-specific spectral lines.