Ferromagnetic spin coupling in the chromium dimer cation: Measurements by photodissociation spectroscopy combined with coupled-cluster calculations.

The magnetic coupling of the chromium dimer cation, Cr2+, has been an outstanding problem for decades. An optical absorption spectrum of Cr2+ has been obtained by photodissociation spectroscopy in the photon-energy range from 2.0 to 5.0 eV. Besides, calculations have been performed by the equation-of-motion coupled-cluster singles and doubles method for vertical excitation of the species. Their coincidence supports our assignment that the ground electronic state exhibits a ferromagnetic spin coupling, which is contrary to those of neutral and negatively charged dimers, Cr2 and Cr2- , in their lowest spin states. [ABSTRACT FROM AUTHOR]