The Discovery of a New Class of Magnetic Superhalogens

We report the discovery of a new class of magnetic superhalogens and their unusually stable molecular anions. These are formed when a hot plume of manganese atoms is cooled through collisions with an inert gas in the presence of chlorine atoms. The anions, with a composition of (Mn$_{x}$Cl$_{2x+1})^{-}$ (x = 1, 2, 3. . . ), appear as prominent (magic) peaks in mass spectra. Using calculations based on density functional theory and experiments utilizing anion photoelectron spectroscopy, we traced the origin of their unusual stability to the half-filled d-shell of the Mn atoms in anionic clusters and the large electron affinities of their neutral counterparts. The calculated and measured electron affinities are almost twice as high as that of the chlorine atom. However, unlike conventional superhalogens which are non-magnetic and consist of a single metal atom at the core surrounded by halogen atoms, the superhalogens discovered here are magnetic and have (MnCl$_{2})_{x}$ moiety as a core to which a chlorine atom is attached. In addition, our calculations show that Mn atoms carry large magnetic moments and Mn$_{x}$Cl$_{2x+1}$ superhalogen moieties can serve as building blocks of a new category of salts with magnetic properties.