10 Nov 2022
10 Nov 2022
Status: this preprint is currently under review for the journal MR.

The effect of the zero-field splitting interaction in light-induced pulsed dipolar EPR spectroscopy

Andreas Scherer, Berk Yildirim, and Malte Drescher Andreas Scherer et al.
  • Department of Chemistry and Konstanz Research School Chemical Biology, University of Konstanz, 78457 Konstanz, Germany

Abstract. Laser-induced magnetic dipole spectroscopy (LaserIMD) and light-induced double electron-electron resonance spectroscopy (LiDEER) are important techniques in the emerging field of light-induced pulsed dipolar EPR spectroscopy (light-induced PDS). These techniques use the photoexcitation of a chromophore to the triplet state and measure its dipolar coupling to a neighboring electron spin, which allows the determination of distance restraints. LaserIMD and LiDEER were so far analyzed with software tools that were developed for a pair of two S = 1/2 spins and neglect the zero-field splitting interaction (ZFS) of the excited triplet. Here, we show that the ZFS cannot be neglected in light-induced PDS, as it has an effect on the shape of the dipolar trace. For a detailed understanding of the effect of the ZFS, a theoretical description for LaserIMD and LiDEER is derived, taking into account the non-secular terms of the ZFS. Simulations based on this model show that the ZFS leads to an additional decay in the dipolar trace in LaserIMD. This effect is not so pronounced in Q-band but can be quite noticeable for lower magnetic fields like in X-band. Experimentally recorded LiDEER and LaserIMD data confirm these findings and show that the ZFS is an important parameter that needs to be considered for the accurate description of light-induced PDS.

Andreas Scherer et al.

Status: open (until 08 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on mr-2022-20', Alexander G. Maryasov, 11 Nov 2022 reply
    • AC1: 'Reply on CC1', Andreas Scherer, 13 Nov 2022 reply
  • RC1: 'Comment on mr-2022-20', Gunnar Jeschke, 24 Nov 2022 reply

Andreas Scherer et al.

Andreas Scherer et al.


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Short summary
Light-induced pulsed dipolar EPR spectroscopy (PDS) is an emerging field that uses photoexcited triplet states to determine distance restraints in the nanometer range. So far, light-induced PDS data have been analyzed with methods that were developed for techniques that do not invoke triplets. Here, we provide a new theoretical description that takes the full nature of the triplet state into account and demonstrate that it leads to more accurate fits of experimental data.