Model and calculation of rate constants of nonradiative T-S intersystem conversion: Test by example of naphthalene and its chlorine derivatives

Abstract

For in-plane spin states (s = z, y), the rate constants Kdgs of the nonradiative energy degradation T1 ⇝ S0 of the lowest triplet T1 state of naphthalene (NPH) and its dichloro-substituted derivatives at positions 1,4- and 2,3- of the molecule (1,4-NPH and 2,3-NPH) are calculated. A simple model is proposed for calculations that is based on the nonadiabatic approximation and uses all the out-of-plane vibrational modes of the molecule as promoting vibrational modes. As a result of calculations, the dependences of the rate constants Kdg and Kdgs on the positions of chlorine atoms in the molecule are obtained, which are consistent with the known data of magnetooptical measurements. The inversion of the ratio Kdgz: Kdgy in the 1,4-NPH and 2,3-NPH molecules is established.