Temperature Dependence of Electron Spin Relaxation of 2,2-Diphenyl-1-Picrylhydrazyl in Polystyrene
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The electron spin relaxation rates for the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) doped into polystyrene were studied by inversion recovery and electron spin echo at X-band and Q-band between 20 and 295 K. At low concentration (340 μM, 0.01 %), spin–lattice relaxation was dominated by the Raman process and a local mode. At high concentration (140 mM, 5 %), relaxation is orders of magnitude faster than at the lower concentration, and 1/T 1 is approximately linearly dependent on the temperature. Spin lattice relaxation rates are similar at X-band and Q-band. The temperature dependence of spin echo dephasing was faster at about 140 K than at higher or lower temperatures, which is attributed to a wagging motion of the phenyl groups.
KeywordsElectron Paramagnetic Resonance DPPH Relaxation Rate Dynamic Nuclear Polarization Spin Lattice Relaxation Rate
The partial support of this work by NIH NIBIB grant EB002807 (GRE and SSE) is gratefully acknowledged.
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