EPR of Cu2+ doped in NH4Br: Orthorhombic centre

Cu2+-doped ammonium bromide, grown in acidic solution (pH approximate to 0), has been studied by electron paramagnetic resonance in the range 294-77 K. A new Cu2+ centre has been found with spin Hamiltonian parameters almost constant with temperature. At 294 K g(x) = 2.313 +/- 0.005, g(y) = 2.144 +/- 0.005, g(z) = 2.046 +/- 0.005, A(x) 162 +/- 3, A(y) = 0 +/- 5, A(z) = 13 +/- 3, A(x)' = 0 +/- 2 and A(y)' = 78 +/- 3 (A is given in units of 10(-4) cm(-1)). A model with Cu2+ ion at the centre of a Br- square, with two adjacent vacancies at the NH4+ sites, is proposed. (C) 1997 Elsevier Science Ltd.