Berlin 2014 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 4: Theory 1: Molecular Dynamics
MO 4.3: Vortrag
Montag, 17. März 2014, 14:45–15:00, BEBEL SR144
Coherent electron hole dynamics near a conical intersection — Henry Timmers1, •Zheng Li2, 3, Niranjan Shivaram1, Robin Santra2, 3, Oriol Vendrell2, and Arvinder Sandhu1 — 1Department of Physics, University of Arizona, Tucson, AZ, 85721 USA — 2Center for Free Electron Laser Science, DESY, Notkestraße. 85, D-22607 Hamburg, Germany — 3Department of Physics, University of Hamburg, D-20355 Hamburg, Germany
The motion of an electron hole (positive charge) across a molecule is vital for many chemical and biological phenomena. These quantum mechanical charge dynamics are mediated through complex electron-electron and electron-nuclear interactions. The investigation of such processes is challenging since it requires preparing and monitoring a coherent superposition of quantum states in the ionized molecule. We create a coherent hole wavepacket near a conical intersection in photoionized CO2 and study the coupled nuclear-hole dynamics in real-time by employing a femtosecond extreme-ultraviolet (XUV) pump and near infrared (NIR) probe. We directly observe the oscillation of the electron hole density between σ and π character, driven by the coupled bending and asymmetric stretch vibrations of the molecule, and provide a detailed theoretical investigation of the observed phenomena. We find that the degree of electronic coherence for the electron hole motion decreases with time due to Coulombic interaction of the excited photoelectron with the ion and we measure the rate of this decohering process.