Conical intersections induced by the Renner effect in polyatomic molecules

Characterizing and localizing electronic energy degeneracies is important for describ-ing and controlling electronic energy flow in molecules. We show, using topological phase considerations that the Renner effect in polyatomic molecules with more than 3 nuclei is necessarily accompanied by 'satellite' conical intersections. In these intersections the non-adiabatic coupling term is on the average half an integer. We present ab-inito results on the tetra-atomic radical cation C2H2+ to demonstrate the theory