Importance of spin-orbit coupling for the assignment of the photodetachment spectra of AuX₂^- (X = Cl, Br, and I)

Recently, photodetachment spectra of AuX₂^-, X = Cl, Br, and I, have been reported [D. Schröder et al., Angew. Chem. Int. Ed. 2003, 42, 311] followed by a scalar-relativistic theoretical study of the assignment of these spectra [B. Dai, J. Yang, Chem. Phys. Lett. 2003, 379, 512]. Herein, the photodetachment spectra of the title molecules are reassigned, taking spin-orbit coupling into account and employing relativistic-effective core potentials for gold and the halogen atoms. The composition of the AuX ₂ electronic states are further analyzed in terms of scalar-relativistic electronic states. The relevance of spin-orbit coupling in the spectroscopy of heavy elements is emphasized by comparing the results of this work with experiment and with other scalar-relativistic theoretical studies.