Seams near seams:: The Jahn-Teller effect in the 1E state of N3+

The E-1(') electronic state of cyclic N-3(+) arising from the singly excited electron configuration e('3)e(') is studied using multireference configuration interaction wave functions and a quadratic Jahn-Teller Hamiltonian determined from those calculations. It is shown that these two states have both a symmetry-required seam of conical intersections at D-3h geometries and three proximal symmetry equivalent C-2v seams, located on a circle with radius rho(0) from the D-3h intersection. rho(0), a function of Q(s), the breathing mode, is quite small but only attains a value of zero at Q(s)(crit)=1.252 A, resulting in a confluence or intersection node of the three C-2v seams with the D-3h seam. At this point only, g=parallel to g(Q(s))parallel to, the norm of half the energy difference gradient, the linear Jahn-Teller term, vanishes and the intersection is of the Renner-Teller type. The close proximity of the previously unreported C-2v seams to the D-3h seam over the range of Q(s) considered is a consequence of the small values of g, compared to the quadratic Jahn-Teller term. The present analysis has important implications in the study of Jahn-Teller effects in ring systems and provides insight into a recent report that characterized this D-3h seam as a Renner-Teller or glancing intersection. (c) 2007 American Institute of Physics.