A comparative study of electron spin decoherence at X- and W-band frequencies as a function of local disorder

• We investigated geometrical frustration in solid ethanol by X- and W-band EPR.
• We show frequency dependence of electron spin decoherence as a function of disorder.
• We propose nuclear spectral diffusion as an indicator of the extent of frustration.

The impact of geometrical frustration on electron spin decoherence pathways is studied by electron paramagnetic resonance spectroscopy (EPR) at X- and W-band frequencies. The glassy and crystalline state of solid ethanol served as a simple model of two extreme realizations of host molecular packing probed by relaxation behavior of incorporated paramagnetic nitroxyl radical TEMPO. The specific molecular dynamics is revealed as arising from the local disorder of the environment, suggesting the importance of nuclear spin bath coupling with the electron spin. It is proposed that spectral diffusion might be useful indicator of the extent of frustration in disordered/glassy matrices.