A Study of a Manganese Paramagnetic Center in Irradiated NaCl : Mn++ Crystals

An E.P.R. study of Mn ++ -doped NaCl irradiated at liquid nitrogen temperature was made at the X- and K-band frequencies. A new paramagnetic manganese center with the principal axes of [100], [010] and [001] and in the extraordinary large crystalline field was found. Rhombic field parameters are obtained to be D =-1450±20 and E =107±10 gauss by analyzing the K-band spectra. Computer diagonalization of the matrix of the spin Hamiltonian including the Zeeman and crystalline field energies is made and the observed X-band spectra are explained qualitatively. Broadening of the line width takes place as the temperature is raised, giving an activation energy of (0.32±0.05) eV. It is considered that the observed spectra are associated with the complex of an Mn ++ and an interstitial halogen ion, and a tentative model is suggested which accounts for the observed experimental results.