Anisotropy of the electron spin-lattice relaxation. PO 3 2- radical in glycinium phosphite gly·H 3 PO 3 crystal

Electron spin-lattice relaxation has been measured for PO radical in glycinium phosphite gly·H PO crystal and its deuterated analogue in temperature range 40-300 K. Angular dependence of the relaxation rate was measured in three crystal planes at room temperature. The Debye cut-off temperature has been calculated as Θ = 97 K, which indicates that the temperature dependence of 1/T is governed by radical local vibrations localized in optical phonon modes range. Theories of possible 1/T angular dependence are reviewed. The anisotropy of spin-lattice relaxation rate in our crystal is assumed to be a result of local magnetic field fluctuations due to electron-proton dipolar coupling. Theoretical evaluation of 1/T were performed for coupling with protons at distances up to 0.46 nm. Not perfect agreement was found with motion correlation time τ = 2·10 s.