Formulation of the double differential and other cross-sections for the ClHCl^- photodetachment process

The theory of dissociative photodetachment of closed-shell linear triatomic molecular ions is developed with emphasis on ClHCl^-. The electronic states are described using a valence bond method, and the detachment process is assumed to be direct, and to produce a scattered electron in either an s or d type continuum orbital. The neutral ClHCl is assumed to be produced in either a ²Σ or a ²Π state, and its dissociation dynamics includes full coupling between electronic, vibrational, rotational and fine-structure states, and the possibility of dissociation into more than one product arrangement. A completely general expression for the electronic transition moment is used, and Franck-Condon approximations are not invoked. Simplifications to the rigorous expression for the double differential cross-section for dissociative photodetachment are considered, leading to an expression for the degeneracy averaged integral cross-section (summed over all magnetic quantum numbers) that is amenable to explicit evaluation based on wavefunctions from reactive scattering calculations.