ESR and Electron Spin Echo Studies of Spin-Lattice Relaxation of Hydrazinium Radical in Li(N2H5)O4 Single Crystal
P. Morawski, S.K. Hoffmann, W. Hilczer and J. Goslar
Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland
Received: January 13, 1997; in final form: April 14, 1997
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A hydrazinium ṄH-NH3+ radical was identified by ESR in γ-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 parameters (in mT): aN1 = 1.93, aN2 = 0.80, aH1 = 2.50, aH1' = 0.48 (NH3), and aH2 = 1.40 (adjacent molecule). The radiation defects containing unpaired electrons do not influence much the protonic conductivity along the hydrazine molecule chains in the crystal. It confirms a tunelling mechanism of the conductivity activated by NH2-group rotation. Spin-lattice relaxation time T1 varies strongly with temperature in the range from 100 ms (10 K) to 90 μs (170 K) and is governed by spectral diffusion (1/T1 ∝ T2) and a Murphy-type mechanism (1/T1 ∝ cosech(Δ/T)) with Δ = 150 cm-1. A distribution of the spin-relaxation times was observed with temperature independent dispersion parameter β = 0.76.
DOI: 10.12693/APhysPolA.91.1121
PACS numbers: 61.80.Ed, 76.30.Rn