Frankfurt 2006 – scientific programme

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MO: Molekülphysik

MO 51: Molecular Quantum Control

MO 51.4: Talk

Thursday, March 16, 2006, 11:25–11:40, H12

Enhancement of Population Transfer and Coherent Vibrations in Nile Blue (LD 690) with Phase Modulated Femtosecond Pulses — •Jürgen Hauer, Tiago Buckup, and Marcus Motzkus — Philipps-Universität, Physikalische Chemie, D-35032 Marburg, Germany

Coherent control of vibrational modes is essential for manipulating photochemisty on ground and excited states. We present an open loop control scheme for mode selective excitation and also for population transfer to the excited state of a dye molecule (Nile Blue). In a spatial light modulator, a sinusoidal modulation is applied in order to obtain pulse trains with well defined spacings between the sub-pulses. We show that these pulse trains allow for a more effective population transfer to the excited state than a Fourier limited pulse of equal energy. Independently thereof, the amplitude of the skeleton mode in Nile Blue at 600 cm-1 is also increased by a factor of up to 1.5, depending on the pump wavelength. In order to explain the nature of the observed enhancement effect, we compare the amplification factor of pulse trains compared to unshaped pulses at different excitation wavelengths. We also perform a chirp scan on the pump pulse, indicating that either ground or excited state wavepackets are observed, depending on the pump wavelength.