Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 13: Probing Vibrations

MO 13.6: Talk

Thursday, March 9, 2017, 12:30–12:45, N 6

Enhancement of Vibrational Coherence by Excitation with Chirped Multipulses — •Elisabeth Brühl, Tiago Buckup, and Marcus Motzkus — Physikalisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Germany

To steer photochemical reactions into selected channels, the tailoring of molecular vibrations is a fundamental control knob. Vibrational coherence of the ground state can be manipulated by using chirped pump pulses via intrapulse impulsive Raman scattering [1]. Additionally, electronic near-resonant excitation with multipulses has been shown to enhance vibrational coherence in the excited state [2]. In this work, these two methods of mode selective control are combined to study the interplay of chirped pulses and multipulses on vibrational coherence and population in the electronic excited as well as in the ground state over a range of excitation spectra. This is demonstrated by systematic phase shaping of the excitation pulse in transient absorption of dye molecules. Our control results of population and vibrational coherence show a strong dependence on the excitation detuning. For example, a blue-detuned multipulse enhances the vibrational coherence and its influence linearly adds to the one of the chirp. The effects for resonant and red-detuned excitation, on the other hand, are in general less pronounced and do not follow the same trend as for blue-detuned. For a better understanding of the underlying process and the assignment of ground and excited state contributions a numerical model is developed.

[1] Bardeen et al., JPC A 1998, 102, 17.

[2] Buckup et al., JPB 2008, 41, 074024.