Formation of electronic coherences in conical intersection-mediated dynamics

We consider the formation of vibrationally-induced transient electronic coherences driven by conical intersection (CI)-mediated population transfer between two electronic states. By invoking fundamental symmetry arguments, we identify several important factors which modulate the magnitude of these electronic coherences. We consider the sub-cases where the two electronic states have either the same or different Abelian point group symmetry at the Franck-Condon geometry. For the different symmetry case, due to the inherent symmetry of the molecular Hamiltonian, significant electronic coherences are unlikely to form. In contrast, for electronic states of the same symmetry, large magnitude electronic coherences can form. However, the magnitude of these coherences is highly dependent on the topography of the CI. These results offer a guide to experimental studies of electronic coherences which may (or may not) be induced by nuclear motion in the vicinity of a CI, as well as to ab initio simulations which are employed to simulate them.