Eur. Phys. J. B (2018) 91: 141
https://doi.org/10.1140/epjb/e2018-90117-6

Regular Article

When the exact factorization meets conical intersections...^★

¹ Laboratoire de Chimie Physique, UMR 8000 CNRS/University Paris-Sud, 91405 Orsay, France
² Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK

^a e-mail: basile.f.curchod@durham.ac.uk

Received: 2 March 2018
Received in final form: 2 May 2018
Published online: 2 July 2018

Abstract

Capturing nuclear dynamics through conical intersections is pivotal to understand the fate of photoexcited molecules. The concept of a conical intersection, however, belongs to a specific definition of the electronic states, within a Born–Huang representation of the molecular wavefunction. How would these ultrafast funneling processes be translated if an exact factorization of the molecular wavefunction were to be used? In this article, we build upon our recent analysis [B.F.E. Curchod, F. Agostini, J. Phys. Chem. Lett. 8, 831 (2017)] and address this question in a broader perspective by studying the dynamics of a nuclear wavepacket through two types of conical intersections, differing by the strength of their underlying diabatic coupling. Our results generalize our previous findings by (i) showing that the time-dependent potential energy surface smoothly varies, both in time and in position, between the corresponding diabatic and adiabatic potentials, with sometimes more complex features if interferences are observed, (ii) highlighting the non-trivial behavior of the time-dependent vector potential and the fact that it cannot be gauged away in general, and (iii) justifying some approximations employed in the derivation of a mixed quantum/classical scheme based on the exact factorization.