Theory of electronic circular dichroism lineshapes

A microscopic, quantum field theory of lineshapes for electronic circular dichroism spectra is presented. A simple, model Hamiltonian for a single impurity in a crystal is considered. In this formalism, electron-photon coupling terms contribute directly to the magnetic transition dipole moment. Lineshape functions for absorbance and circular dichroism spectra are derived. Electronic circular dichroism spectra contain vibronic contributions which do not appear in absorbance spectra. This treatment does not require perturbation theory to obtain the vibrational contribution to the circular dichroism lineshape.