Photoionisation can create a coherent superposition of electronic states and therefore initiates electronic dynamics in atoms and molecules. Observing and controlling this experimentally is a target of attosecond spectroscopy. Theoretical studies of pure electron dynamics at a fixed nuclear geometry have demonstrated oscillatory charge migration [1-2].

Using a CASSCF implementation of the Ehrenfest method [3], we can study the evolution of a non-stationary electronic wavefunction for fixed atomic nuclei, and where the nuclei are allowed to move, to investigate the differences [4]. We choose the benzene cation as a prototype because ionising the neutral species leads to a Jahn-Teller degeneracy between ground and first excited states of the cation.

Our calculations have explicitly shown how changing the initial electronic wavefunction can control nuclear dynamics for an ionised molecule where multiple electronic states are close in energy. We have also been able to show how chemical substitution of the benzene cation affects the outcome of the electronic dynamics.

[1] F. Remacle, R. D. Levine, Z. Phys. Chem. 221, 647-661 (2007)

[2] J. Breidbach, L. S. Cederbaum, J. Chem. Phys. 118, 3983-3996 (2003)

[3] M. Vacher, D. Mendive-Tapia, J. Bearpark, M. A. Robb, Theo. Chem. Acc. Accepted (2014)

[4] D. Mendive-Tapia, M. Vacher, M. J. Bearpark, M. A. Robb, J. Chem. Phys. 139, 044110 (2013)