Electronic structure and photoelectron spectroscopy of manganese dihalides from quantum chemical methods and Dyson orbitals

Accurate treatment of electron correlation and spin-orbit coupling is essential for understanding the electronic structure and spectroscopy of high-spin, open-shell transition metal dihalides. The experimental photoelectron spectra of MnX₂, X = Cl, Br, I, have been interpreted on the basis of multi-configurational ab initio electronic structure calculations. The intensity of the photoelectron bands have been calculated from the norms of the Dyson orbitals, which represent the transition probability to a particular ionic state from a given starting state. The present study provides a detailed account of the contribution of the one- and two-electron transitions in the experimental photoelectron spectra of the title molecules and outlines the nature of the photoelectron bands in terms of the closely spaced quintet and septet states of the cationic species.