Hannover 2013 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 13: Quantum Chemistry and Molecular Dynamics II
MO 13.9: Vortrag
Dienstag, 19. März 2013, 16:00–16:15, F 107
Ultrafast Energy Transfer to Liquid Water by Short and Intense THz Pulses — •Pankaj Kumar Mishra1,2,3, Oriol Vendrell1,3, and Robin Santra1,2,3 — 1Center for Free-Electron Laser Science, DESY,Hamburg, Germany — 2Department of Physics, University of Hamburg, Hamburg, Germany — 3Centre for Ultrafast Imaging, University of Hamburg,Hamburg, Germany
Water is the most common solvent in which chemical reactions take place. In recent years it is becoming clear that low frequency modes in the THz domain play an important role in the structure and dynamics of water. Recently, the possibility to generate sub-ps and very intense THz pulses at free-electron lasers in full synchronization with the x-rays opens the possibility to time-resolved investigations of transient states of water and of molecular species dissolved in it. Here, we investigate the response of liquid water to one-cycle, 200fs long THz pulses spectrally centered at about 3THz. The THz pulse does not target any particular modes of the liquid. At an intensity of about 1010 W/cm−2, we find that the pulse transfers energy mostly to translational modes of the water monomers along the polarization axis of the electric field. In a time-scale of 500fs to 1ps the energy redistributes to hindered rotational modes first, and to intramolecular vibrations last. This implies that the energy supplied by the THz can potentially activate chemical processes long before the large amount of energy supplied leads to volume increase and vaporization of the medium. In this study, we have used CP2K package for Ab-Initio Molecular Dynamics.