On the role of conical intersections in photodissociation. III. the case of hydroxylamine

Conical intersections of two states of the same symmetry are usually considered rare and are frequently ignored in the treatment of nonadiabatic processes. This work addresses the veracity of this assumption. The existence of conical intersections of two states of the same symmetry is considered for the four lowest electronically excited states of hydroxylamine NHOH using configuration interaction wave functions. The existence of "same symmetry" conical intersections is demonstrated and their role in the photodissociation process NHOH→NH+OH investigated. Although the ground electronic state has C symmetry (with two equivalent hydrogens) it is argued that conical intersections corresponding to nuclear configurations far removed from C symmetry play a role in the photodissociation