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Probing the differences for TEMPO incorporated in glassy & crystalline ethanol using constant time CPMG experiment

Glassy and crystalline solid ethanol are used as a model systems to study disorder in the material. It is probed by the hyperfine interaction of the electron spin from the incorporated paramagnetic nitroxyl radical TEMPO. Nuclear spectral diffusion from host matrix protons is the dominant mechanism of electron spin decoherence of TEMPO incorporated in two realizations of solid-state environment of ethanol and it is proposed as a descriptor of the extent of disorder present in the system [1, 2]. It can be suppressed when applying special multiple-pulse sequence developed for the dynamical decoupling control of the central spin. The effect is much more pronounced in glassy than crystalline ethanol, the state exhibiting larger disorder/frustration. Since the phase memory relaxation time of the paramagnetic center increased linearly with the increase in the number of the applied refocusing pulses, the effect of the extent of disorder could be described numerically for this specific model system. [1] M. Kveder, D. Merunka, M. Jokić, B. Rakvin, J. Non-Cryst. Solids 354 (2008) 5201 [2] M. Kveder, B. Rakvin, M. Jokić, E. Reijerse, J. Non-Cryst. Solids 414 (2015) 27

Glassy state ; pulse EPR ; disorder ; CPMG

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