2004 -02 -04
10 :15 at ML J 21

Shedding light into conical intersection topology

Daniele Passerone

Computational Laboratory (CoLab), ETH Zurich

The picture of a general class of photochemical reactions can be provided in terms of evolution of an excited-state species toward a conical intersection (CI) that acts as photochemical decay channel. A CI is defined as a ``point'' (it is indeed an hypersurface) in nuclear coordinate space at the confluence of two potential energy surfaces. Its existence implies the possibility of radiationless decay of a chemical species, and can be assumed more likely to be the rule than an exception. I will introduce in this seminar a novel method for investigating these particular regions of the energy surface where ground state and excited state energies are degenerate (T. Laino and D. Passerone, Chem. Phys. Lett., submitted). A connection between quantum chemistry methods and a new molecular dynamics algorithm allows finite-temperature simulations which allow a more efficient exploration of a CI with respect to traditional static calculations. As a showcase for the method I discuss the CIs of ethylene and I show the analog of a minimum energy path calculation restricted to the zero gap region.