Intensity of singlet-triplet transitions in C-60 fullerene calculated on the basis of the time-dependent density functional theory and taking into account the quadratic response

摘要

The singlet-singlet and triplet-triplet absorption spectra of C-60 fullerene are calculated using the density functional method and taking into account the theory of linear and quadratic responses. The B3LYP density functional and the 6-31G and 3-21G atomic basis sets are used. The calculations are performed using the D-2h and D-5d symmetry groups, although the real symmetry of the ground state is described by the I-h symmetry group. The matrix elements of the operator of the spin-orbit coupling are calculated and the probabilities of some singlet-triplet transitions are estimated. Taking into account the data in the literature on vibronic interactions of vibrations of the t(1u), t(2u), g(u) and h(u) symmetry species, the radiative lifetime of the 1(3)T(2g) → 1(1)A(g) phosphorescence was estimated to be 45 s. The fact that this time proved to be considerably greater than the experimentally observed total lifetime of the triplet testifies to a fast nonradiative deactivation of the lowest triplet state of C-60 fullerene and agrees with a low phosphorescence intensity. The zero-field splitting of some triplets and the intensities of magnetic dipole transitions are discussed. (C) 2005 Pleiades Publishing, Inc.