ESR AND ELECTRON-SPIN ECHO STUDIES OF SPIN-LATTICE RELAXATION OF HYDRAZINIUM RADICAL IN LI(N2H5)SO4 SINGLE-CRYSTAL

A hydrazinium N (over dot)H-NH3+ radical was identified by ESR in gamm a-irradiated Li(N2H5)SO4 single crystal. Unpaired electron is strongly localized on the nitrogen atom as compared to hydrazinium radicals in other crystals. Angular variations of the multicomponent ESR spectra and computer calculations gave the isotropic hyperfine coupling parame ters (in mT): a(N1) = 1.93, a(N2) = 0.80, a(H1) = 2.50, a(H1') = 0.48 (NH3), and a(H2) = 1.40 (adjacent molecule). The radiation defects con taining unpaired electrons do not influence much the protonic conducti vity along the hydrazine molecule chains in the crystal. It confirms a tunnelling mechanism of the conductivity activated by NH2-group rotat ion. Spin-lattice relaxation time T-1 varies strongly with temperature in the range from 100 ms (10 K) to 90 mu s (170 K) and is governed by spectral diffusion (1/T-1 proportional to T-2) and a Murphy-type mech anism (1/T-1 proportional to cosech(Delta/T)) with Delta = 150 cm(-1). A distribution of the spin-relaxation times was observed with tempera ture independent dispersion parameter beta = 0.76.