Entanglement of the molecular photodissociation products at avoided crossings and conical intersections

This is a quantum mechanical study of the entanglement between pyrrolyl radical and the H-atom formed in the photodissociation of pyrrole. The parent molecule is photoexcited into the low lying ${}^1\pi {\sigma }^{\ast }$ states interacting with the ground electronic state via avoided crossings or conical intersections. The entanglement, studied in the time independent and the time dependent frameworks, is quantified using the von Neumann entropy which can be expressed in terms of the normalized internal state distributions of the pyrrolyl product. It is demonstrated that the von Neumann entropy is sensitive to the coupling between two electronic states and is substantially affected by Fano resonances in the dissociating molecule. The entropy generated at a conical intersection is generally larger than at an avoided crossing, although the main qualitative features are similar in both cases.