Vibronic Fine Structure of the Line Shape for E→T Transition: The GRl Band in Diamond

Abstract

An optical line shape for E→T₂ transition in tetrahedral symmetry has been calculated for the case where both the ground and the T₂ excited states are coupled to an e vibrational mode. The effect of quadratic Jahn-Teller coupling in the ground state on vibronic fine structure is investigated. The calculated result has been compared with the GRl absorption band in diamond. The origin of a 40 meV sideband observed experimentally has been explored within the framework of the Jahn-Teller interaction following the suggestion by Davies and Foy. It has been shown that its energy position and relative intensity can be explained, if the quadratic coupling of e-t in the T₂ excited state is taken into account.