Multiconical intersections and nondegenerate ground state in E ⊗ e Jahn-Teller systems

We have investigated the E x E Jahn-Teller problem with large quadratic coupling. Our results reverse the paradigm that, in E x e Jahn-Teller systems, the ground vibronic state should be the same as that of the initial doubly degenerate electronic E term. The E vibronic state is the ground state for small quadratic coupling when the dominant tunneling path between the potential surface minima encircles one central conical intersection. whereas for large quadratic coupling it goes around four conical intersections and the ground state becomes nondegenerate.