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MO: Fachverband Molekülphysik

MO 9: Femtosekundenspektroskopie 3

MO 9.4: Vortrag

Dienstag, 3. März 2009, 17:15–17:30, VMP 6 HS-F

Pulse train excitation- dynamics and spectroscopy — •Judith Voll and Regina de Vivie-Riedle — LMU Department Chemie, Butenandt-Str. 11, 81377 München, Germany

Optical control of molecular and biological systems aims at steering reactions by special shaped laser pulses as well as at spectroscopic informations about the participating pathways. In several control experiments sequences of pulses, separated in time, were obtained as best results to control the outcome of a light induced reaction. Comparable pulse sequences can be obtained by parameterisation, using a sinusoidal modulator mask, Φ(ω) = a sin(bω+c), leading to a train of pulses with defined phase relation [1]. Successful control application of pulse trains have been demonstrated for energy transfer in LH₂ [2], a light-harvesting complex, and for enhancement of ground state modes of β-carotene [3].

Based on quantum dynamical calculations on a model of β-carotene, we present systematic studies on the electronic excitation mechanisms due to pulse trains in the low energy regime. We follow the induced wave packet dynamics on the excited states including the process of internal conversion. We discuss and explain the effect of the individual pulse parameters b and c. Relating the pulse parameters to the system response, we outline a strategy for the use of pulse trains in spectroscopy and signal processing.

[1] T. Hornung et al.,Chem. Phys. Lett., 326, (2000) 445.

[2] J. L. Herek et al., Nature 417, (2002) 533.

[3] J. Hauer et al.,Chem. Phys. Lett., 421, (2006) 523.