Regensburg 2025 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 17: Poster Session II

BP 17.60: Poster

Dienstag, 18. März 2025, 18:00–20:30, P4

Hyperfine spectral diffusion in pulse EPR: theory and applications — •Sergei Kuzin^1,2, Gunnar Jeschke¹, and Maxim Yulkov¹ — ¹ETH Zurich, Zurich, Switzerland — ²MPI for Multidisciplinary Sciences, G\"ottingen, Germany

Hyperfine interaction with nuclear spin bath and nuclear spin-spin interaction often dominate phase memory times of the electron spins in spin-diluted solids at cryogenic temperatures. Such an spin-ensemble effect also manifests is different EPR experiments as spectral diffusion.

Here, we present a new pulse EPR method called intermolecular hyperfine relaxation-induced dipolar modulation enhancement (ih-RIDME). This technique allows to investigate kinetics of spectral diffusion in amorphous solids. The sensitivity range of ih-RIDME lies within 1-3~nm around the spin centre. This makes it a powerful tool to probe nuclear spin arrangement at intermediate electron-nuclear distances. The quantification in ih-RIDME is based on a developed mathematical model of spectral diffusion resulting in a diffusion-like equation. With its help, ih-RIDME allows to quantify heterogeneous systems with a distribution of local proton densities.

We discuss the applications of ih-RIDME in dynamic nuclear polarization, structural biology, spin-labeled macromolecules and soft matter study.

Keywords: EPR; relaxation; phase memory time; hyperfine coupling