ESR studies of Cl<inf>2</inf>^− (V<inf>k</inf>) centre trapped in irradiated Ca(ClO<inf>3</inf>)<inf>2</inf>.2H<inf>2</inf>O single crystals

A Cl2− centre has been trapped in X or γ-irradiated Ca(CaClO3)2.2H2O single crystals at 298 K, when the irradiated crystals were illuminated with ultra-violet light (360 nm). This centre is formed at the expense of ClO2centres in this crystal. This Cl2− centre is trapped at two magnetically inequivalent sites in the crystal lattice and these sites become equivalent when the static magnetic field is parallel or perpendicular to the b axis. At many orientations this centre reveals ‘super-hyperfine’ interaction with a proton (I = ½) of the water of crystallization. The magnetic parameters are close to those observed in alkali chlorides and the E.S.R. spectrum has been fitted to an orthorhombic spin hamiltonian. The principal g values are gxx = 2.035, gyy = 2.033 and gzz = 2.000 and those of the A values are Axx= 15.0, Ayy = 31.0 and Azz = 109.0 G. The shfs parameters are Aǁ’ = 5.0 A˔' = 1.0 G. The VKcentre trapped in this lattice is exceptionally stable at room temperature. © 1975 Taylor & Francis Group, LLC.