Unanticipated confluences of seams of conical intersection: Reinvestigating intersecting potential-energy surfaces using new tools. I. C(3P)+H2

Abstract

Recently a quite unexpected situation has been found in which two distinct seams of conical intersection originating from the same two states—one the accidental intersection of two states of different symmetries and one the accidental intersection of two states of the same symmetry—intersect. These confluences can now be systematically identified using an algorithm that relies solely on information obtained from the symmetry-allowed seam. It is necessary to ask whether, in the absense of such an algorithm, these confluences have been overlooked in the past. In this work the well studied 1 3A″–2 3A″ seam of conical intersection in C(3P)–H2 is reinvestigated using the above noted algorithm with surprising results.