Response Theory Studies of Triplet-State Spectra and Radiative Lifetimes of Naphthalene, Quinoxaline, and Phthalazine

Abstract

Response theory calculations with complete account of spin-orbit coupling (SOC) are performed to predict spectra and radiative lifetimes for triplet states of naphthalene and two of the doubly N-substituted azanaphthalenes, quinoxaline and phthalazine. A quite long triplet-state lifetime for naphthalene is found, about 1 min, which is approximately twice the previously accepted value. For quinoxaline the pure electronic radiative lifetime is considerably shorter, on the order of 1 s, but still longer than the one given experimentally. The large increase of radiative lifetime on going from quinoxaline to phthalazine is well reproduced by the response calculations