Temperature Dependence of Electron Spin Relaxation of 2,2-Diphenyl-1-Picrylhydrazyl in Polystyrene

Abstract

The electron spin relaxation rates for the stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl) 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/T1 is approximately linearly dependent on 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.

The Electron Spin Phase Memory Decay of Stable Radical Embedded in Glassy Solvent Matrices: Nuclear Spin Bath Model

“…The phase memory decay/decoherence profile of embedded paramagnetic centers under standard Hahn spin echo pulse sequence 1 is part of the fundamentals of pulsed/Fourier transform (FT) electron paramagnetic resonance (EPR) 2 . The time scale of decoherence T m limits the lowest frequency/longest distance information observable in the Fourier domain and therefore attracts long lasting interests on it [3][4][5][6][7][8][9][10][11][12][13][14] . This profile also characterizes the capability of the embedded electron spin to remain in pure state when prepared by the π/2 excitation pulse, and therefore attracts significant amount of studies from the solid state quantum computing perspective 15 .…”

“…Current consensus on decoherence of embedded paramagnetic centers states that it is resulted by a combination of contributors. At relatively high temperatures ( 100K) and low electron spin concentration, decoherence in organic solids is usually dominated by the relaxation of hindered segments, most prominently the methyl groups (phenyl rings were also reported) [3][4][5][6][7][8][9][10][11][12][13][14] . When temperatures are low enough to properly freeze these relaxation processes, decoherence under Hahn echo is mainly induced by the interaction between embedded electron spin and the surrounding interacting nuclear spin environment up to nanometer distances, as well as the interaction between electron spins.…”