High-resolution zero electron kinetic energy spectra of the weakly bound ArO- anion are predicted using the method which combines atoms-in-molecule and Rau-Fano models for calculating relative intensities and accurate ab initio interaction potentials. ZEKE spectrum envelope and its temperature variation are shown to be essentially determined by the electronic photodetachment probabilities which are highly selective with respect to the symmetry of the spin-orbit components of anion and neutral electronic states.