Spin-locking in concentration-narrowed OD ESR spectra

Koptyug, Andrey; Saik, Vladimir O.; Animisov, O.A.; Molin, Yu. N.

doi:10.1016/0301-0104(89)80266-6

Cited by 20 publications

(18 citation statements)

References 17 publications

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“…6 Extending previous studies, orientation effects are now investigated in the case of strong B 1 fields. According to the model proposed by Koptyug et al 24 for spin-locking it should not be possible to cause a spin-locking type inversion for parallel fields, an assertion that is tested below, alongside discussion of higher order resonances.…”

Section: Orientation-dependent Effectsmentioning

confidence: 99%

Spin-locking in low-frequency reaction yield detected magnetic resonance

Wedge

Lau

Ferguson

et al. 2013

Phys. Chem. Chem. Phys.

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The purported effects of weak magnetic fields on various biological systems from animal magnetoreception to human health have generated widespread interest and sparked much controversy in the past decade. To date the only well established mechanism by which the rates and yields of chemical reactions are known to be influenced by magnetic fields is the radical pair mechanism, based on the spin-dependent reactivity of radical pairs. A diagnostic test for the operation of the radical pair mechanism was proposed by Henbest et al. [J. Am. Chem. Soc., 2004, 126, 8102] based on the combined effects of weak static magnetic fields and radiofrequency oscillating fields in a reaction yield detected magnetic resonance experiment. Here we investigate the effects on radical pair reactions of applying relatively strong oscillating fields, both parallel and perpendicular to the static field. We demonstrate the importance of understanding the effect of the strength of the radiofrequency oscillating field; our experiments demonstrate that there is an optimal oscillating field strength above which the observed signal decreases in intensity and eventually inverts. We establish the correlation between the onset of this effect and the hyperfine structure of the radicals involved, and identify the existence of 'overtone' type features appearing at multiples of the expected resonance field position.

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Section: Orientation-dependent Effectsmentioning

confidence: 99%

Spin-locking in low-frequency reaction yield detected magnetic resonance

Wedge

Lau

Ferguson

et al. 2013

Phys. Chem. Chem. Phys.

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“…3b). Therefore, the appearance of this feature provides strong evidence that: (i) HFI-ISC processes are occurring in loosely bound inter-CT states with a very small exchange energy (on the order of neV) 25 ; and (ii) the nominally-dark inter-CT states can readily interconvert with the bright intra-1 CT excitons.…”

Section: Resultsmentioning

confidence: 89%

“…Additional information about the HFI-ISC processes occurring in inter-CT states can be obtained by investigating the response of the PLDMR signal to increased microwave intensities, where B 1 is perpendicular to B 0 . When B 1 exceeds the hyperfine field (B HF , typically ~1 mT in organic radicals 20,[29][30][31] ), the rate of the HFI-mediated inter-1 CT 0 /inter-3 CT 0 transitions is reduced as the radical spins begin to precess around B 1 with the same frequency, negating their HFI-induced spin precession frequency difference 25,32,33 . In the absence of an effective spin-mixing process, the spin population now becomes trapped in the initially generated inter-1 CT 0 , leading to spin-locking (Fig.…”

Section: Resultsmentioning

confidence: 99%

Spontaneous exciton dissociation enables spin state interconversion in delayed fluorescence organic semiconductors

et al. 2021

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Engineering a low singlet-triplet energy gap (ΔEST) is necessary for efficient reverse intersystem crossing (rISC) in delayed fluorescence (DF) organic semiconductors but results in a small radiative rate that limits performance in LEDs. Here, we study a model DF material, BF2, that exhibits a strong optical absorption (absorption coefficient = 3.8 × 105 cm−1) and a relatively large ΔEST of 0.2 eV. In isolated BF2 molecules, intramolecular rISC is slow (delayed lifetime = 260 μs), but in aggregated films, BF2 generates intermolecular charge transfer (inter-CT) states on picosecond timescales. In contrast to the microsecond intramolecular rISC that is promoted by spin-orbit interactions in most isolated DF molecules, photoluminescence-detected magnetic resonance shows that these inter-CT states undergo rISC mediated by hyperfine interactions on a ~24 ns timescale and have an average electron-hole separation of ≥1.5 nm. Transfer back to the emissive singlet exciton then enables efficient DF and LED operation. Thus, access to these inter-CT states, which is possible even at low BF2 doping concentrations of 4 wt%, resolves the conflicting requirements of fast radiative emission and low ΔEST in organic DF emitters.

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“…The positive field effect (/on -Ioff > 0) corresponds to the deceleration of ISC by microwave irradiation. This phenomenon is called "spin locking" [8].…”

Section: Resultsmentioning

confidence: 99%

Reaction-yield-detected magnetic resonance in the intra-and intermolecular electron transfer reactions

et al. 1997

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The spin dynamics of the intermediate radical ion pairs formed in the intra-and intermolecular electron transfer reactions between N,N-dimethylaniline and phenanthrene is studied by employing the polymethylene-linked and nonlinked systems. Reaetion-yield-detected magnetic resonance (RYDMR) expe¡ are performed by monitoring the exciplex fluorescente. From the theoretical consideration of the data, we conelude that the lifetime of the radical ion pair in the linked system is shorter than that in the nonlinked system. This tendency is opposite to what is generally observed in linked and nonlinked neutral biradical.

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Spin-locking in concentration-narrowed OD ESR spectra

Cited by 20 publications

References 17 publications

Spin-locking in low-frequency reaction yield detected magnetic resonance

Spin-locking in low-frequency reaction yield detected magnetic resonance

Spontaneous exciton dissociation enables spin state interconversion in delayed fluorescence organic semiconductors

Reaction-yield-detected magnetic resonance in the intra-and intermolecular electron transfer reactions

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