Accurate calculations of second-order vibronic reduction factors for C₆₀ions

Abstract

An effective Hamiltonian containing Jahn-Teller (JT) first-and secondorder vibronic reduction factors (RFs) is a convenient way of modelling the spectroscopic properties of solids and molecules in which vibronic interactions are important. It can act as a bridge between experimental data and basic theory. In particular, second-order RFs can give valuable information on many of the fundamental properties of strongly coupled systems. As interest in the icosahedral fullerene molecules and ions has grown over the last few years, it has become necessary to be able to calculate values for second-order RFs in icosahedral symmetry in terms of more fundamental vibronic coupling parameters. Following on from earlier work on the icosahedral T ⊗ h JT system, we present here results of such calculations of the second-order vibronic RFs for the icosahedral G ⊗ g, G ⊗ h, H ⊗ g and H ⊗ h JT systems. These systems are relevant for the ground and excited states of C 60 anions and cations. The calculations are based on the Franck-Condon approximation followed by additional non-Condon corrections. Previous work has demonstrated that such an approach can give values for the RFs close to those deduced from experiments.