04 Oct 2022
04 Oct 2022
Status: this preprint is currently under review for the journal MR.

Intermolecular contributions, filtration effects and composition of the SIFTER signal

Agathe Vanas1, Janne Soetbeer1, Frauke Diana Breitgoff1, Henrik Hintz2, Muhammad Sajid2, Yevhen Polyhach1, Adelheid Godt2, Gunnar Jeschke1, Maxim Yulikov1, and Daniel Klose1 Agathe Vanas et al.
  • 1Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
  • 2Bielefeld University, Department of Chemistry, Universitätsstrasse 25, D-33615 Bielefeld, Germany

Abstract. To characterise structure and order in the nanometer range, distances between electron spins and their distributions can be measured via dipolar spin-spin interactions by different pulsed electron paramagnetic resonance experiments. Here, for the single frequency technique for refocusing dipolar couplings (SIFTER), the buildup of dipolar modulation signal and intermolecular contributions is analysed for a uniform random distribution of monoradicals and biradicals in frozen glassy solvent by using the product operator formalism for electron spin S = 1/2. A dipolar oscillation artefact appearing at both ends of the SIFTER time trace is predicted, which originates from the weak coherence transfer between biradicals. The relative intensity of this artefact is predicted to be temperature independent, but to increase with the spin concentration in the sample. Different compositions of intermolecular backgrounds are predicted in the case of biradicals and in the case of monoradicals. We compare these predictions to experimental SIFTER traces for nitroxide and trityl monoradicals and biradicals. Our analysis demonstrates a good qualitative match with the proposed theoretical description. The resulting perspectives of quantitative analysis of SIFTER data are discussed.

Agathe Vanas et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on mr-2022-17', Frédéric Mentink-Vigier, 21 Oct 2022
    • CC1: 'Reply on RC1', Maxim Yulikov, 24 Oct 2022
      • RC2: 'Reply on CC1', Frédéric Mentink-Vigier, 24 Oct 2022
  • CC2: 'Comment on mr-2022-17', Mike Bowman, 07 Nov 2022
  • AC1: 'Comment on mr-2022-17', Daniel Klose, 10 Nov 2022
  • EC1: 'Comment on mr-2022-17', Stefan Stoll, 24 Nov 2022
  • EC2: 'A few additional comments', Stefan Stoll, 24 Nov 2022

Agathe Vanas et al.

Agathe Vanas et al.


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Short summary
Nanometer distance measurements between spin labels by pulse EPR techniques yield structural information on the molecular level. Here, backed by experimental data, we derive a description for the total signal of the single frequency technique for refocusing dipolar couplings (SIFTER) showing how the different spin-spin interactions give rise to dipolar signal and background – the latter has thus far been unknown.