Resonance fluorescence involving optically active continua

In this paper we utilize the T matrix formalism of scattering theory for the study of the cross sections specifying optical absorption, resonance fluorescence elastic photon scattering, resonance Raman scattering, and photodissociation for molecules undergoing direct photodissociation or predissociation into a continuum, which carries oscillator strength from the ground state. We have demonstrated that for the special case of radiative interactions with a single molecular continuum explicit expressions can be derived for the Green's function and for the reaction operator, incorporating radiative interactions with one photon states to infinite order. From the complete solution for elastic photon scattering from a dissociative continuum we conclude that the direct radiative corrections are of the order of the "radiative Lamb shift" for the continuum states, and are negligible. The elastic photon scattering cross sections can be expressed in terms of a complex Hubert transform of the Franck-Condon transition density, while the absolute photon scattering quantum yield is ∼10^-7. This treatment has been extended for the study of resonance Raman scattering from a dissociative continuum, where the scattering cross sections can be expressed in terms of absolute squares of complex Hubert transforms of the product of two Franck-Condon vibrational overlaps for bound-continuum transitions. No selection rules for the final vibrational state are exhibited. Finally, we have derived a general solution for photon scattering for a discrete molecular level coupled to an optically active dissociative continuum. The absorption cross section is finite at the interference dip, being determined by the interference function for the continuum states. The quantum yield for resonance fluorescence exhibits a sharp maximum reaching a value of unity at the interference dip where the quantum yield for dissociation vanishes.