Abstract

The formal theory of vibronic coupling in centrosymmetric coordination compounds of the lanthanide complex ions is reviewed on the basis of a crystal field-closure procedure. A formalism is developed on the basis of a weak field compling scheme and it is applicable to any f-f electronic transition. Throughout the course of the present work, the vibronic hamiltonian is expanded to the first order in the nuclear cartesian displacement coordinates. Master equations are derived to account for the transition dipole moments associated with vibronically allowed electronic transition in centrosymmetric lanthanide complex ions. An intensive use of the irreducible tenser algebra is performed to express all the relevant polyelectronic matrix elements in terms of monoelectronic matrix elements. The relevant operators and reduced matrix elements are evaluated, in order to faciltate vibronic intensities calculations in the elpasolite-type systems.