Hannover 2016 – scientific programme
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MO: Fachverband Molekülphysik
MO 18: The Modelling of Molecular Dynamics
MO 18.3: Talk
Thursday, March 3, 2016, 15:00–15:15, f142
Using vibrational dynamics in complex time to investigate the isotope dependence of High-Harmonic Generation in H2 — Manfred Lein and •Marc Ruhmann — Institut für Theoretische Physik and Centre for Quantum Engineering and Space-Time Research (QUEST), Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany
High-Harmonic generation takes place when an atom or molecule is subject to a strong laser field. It is commonly understood as a sequence of ionization, electron excursion and recombination. In the quantum mechanical strong-field approximation (SFA), the times of ionization and recombination, which are real in a classical model, are complex numbers.
In (small) molecules such as H2, the harmonic intensity is approximately proportional to the modulus squared of the vibrational autocorrelation acquired over the electron excursion time. This provides a link between harmonic spectra and vibrational dynamics and explains why heavier isotopes produce more intense radiation.
Here we investigate the ratio of harmonics from D2/H2 by evolving the nuclear wave packets in complex time as given by the SFA. We consider, on the one hand, a reduced-dimensional model where we compare with exact solutions of the TDSE, on the other hand, a three-dimensional model including orientation averaging. We find, for both short and long trajectories, the ratio to be generally lower compared to the classical times and with a different qualitative shape.