Erlangen 2018 – scientific programme
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MO: Fachverband Molekülphysik
MO 11: Theoretical Approaches
MO 11.2: Talk
Tuesday, March 6, 2018, 14:15–14:30, PA 1.150
Conical Intersections and Electronic Coherence: A Novel Path to Steer Nuclear Motion — •Caroline Arnold1,2,3, Oriol Vendrell1,3,4, Ralph Welsch1, and Robin Santra1,2,3 — 1Center for Free-Electron Laser Science, DESY — 2Department of Physics, University of Hamburg — 3The Hamburg Centre for Ultrafast Imaging — 4Department of Physics and Astronomy, Aarhus University
Ultrashort pulses can be used to create coherent superpositions of electronic states in a molecule through photoexcitation. The electronic and nuclear dynamics that are triggered by the excitation are coupled in the vicinity of conical intersections (C.I.), and the Born-Oppenheimer approximation breaks down. This coupled motion provides a possibility for attochemistry, i.e., steering nuclear dynamics by controlling electronic degrees of freedom. In this work, the effect of nuclear dynamics and C.I.s on electronic coherences is investigated employing a two-state, two-mode linear vibronic coupling model. Exact quantum dynamical calculations are performed using the multi-configuration time-dependent Hartree method (MCTDH). It is found that the presence of a C.I. close to the Franck-Condon point can preserve electronic coherence to some extent. Additionally, the possibility of steering the nuclear degrees of freedom by imprinting a relative phase between the electronic states during the photoexcitation process is discussed. It is found that steering the nuclear wavepacket is possible given that a coherent electronic wavepacket embodying the phase difference passes through a C.I. A C.I. close to the Franck-Condon point is thus a necessary prerequisite for attochemistry.