Signature of the geometric phase in the wave packet dynamics on hypersurfaces

We study the nonadiabatic dynamics of an electronic wave packet on two coupled potential energy surfaces. We focus on the difference between two configurations, the presence of a conical intersection (CI) and an avoided crossing (AC). We project the time-dependent dynamics onto the tuning and the coupling modes. For weak intersurface coupling, no significant difference appears. However, significant differences in the deactivation of the wave packet arise for increasing intersurface coupling. Most striking is a strong destructive interference of the two pathways of the wave packet which differ by a factor of π when moving around the CI. This yields to a vanishing of the wave packet in the CI configuration, which does not exist with an avoided crossing. By this, it is straightforward to identify the geometric phase in the wave packet dynamics and to use it to distinguish a CI from an AC configuration.