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

Wedge, Christopher J.; Lau, Jason C. S.; Ferguson, Kelly-Anne; Norman, Stuart A.; Hore, P. J.; Timmel, Christiane R.

doi:10.1039/c3cp52019f

Cited by 13 publications

(21 citation statements)

References 29 publications

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“…There has been considerable theoretical and experimental interest in spin effects that materialize from free radical biological chemical reactions [14], [16], [17], [30]; in particular, the reaction of molecular oxygen activation by reduced flavins, and subsequently, the generation of related active ROS [11], [31]. The Schulten lab have taken the fundamental ideas developed in prior work [16], [17], [23] and applied its significance to an example of biological function in vivo , specifically the role of cryptochrome as a magnetoreceptor in the case of avian magnetic sensing [15].…”

Section: Introductionmentioning

confidence: 99%

Spin Biochemistry Modulates Reactive Oxygen Species (ROS) Production by Radio Frequency Magnetic Fields

et al. 2014

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The effects of weak magnetic fields on the biological production of reactive oxygen species (ROS) from intracellular superoxide (O2 •−) and extracellular hydrogen peroxide (H2O2) were investigated in vitro with rat pulmonary arterial smooth muscle cells (rPASMC). A decrease in O2 •− and an increase in H2O2 concentrations were observed in the presence of a 7 MHz radio frequency (RF) at 10 μTRMS and static 45 μT magnetic fields. We propose that O2 •− and H2O2 production in some metabolic processes occur through singlet-triplet modulation of semiquinone flavin (FADH•) enzymes and O2 •− spin-correlated radical pairs. Spin-radical pair products are modulated by the 7 MHz RF magnetic fields that presumably decouple flavin hyperfine interactions during spin coherence. RF flavin hyperfine decoupling results in an increase of H2O2 singlet state products, which creates cellular oxidative stress and acts as a secondary messenger that affects cellular proliferation. This study demonstrates the interplay between O2 •− and H2O2 production when influenced by RF magnetic fields and underscores the subtle effects of low-frequency magnetic fields on oxidative metabolism, ROS signaling, and cellular growth.

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Section: Introductionmentioning

confidence: 99%

Spin Biochemistry Modulates Reactive Oxygen Species (ROS) Production by Radio Frequency Magnetic Fields

et al. 2014

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“…3). We conclude that theory 3 withstands experimental scrutiny and note that the observations differ fundamentally from conventional spin-locking invoked to describe the inversion of reaction-yield-detected RF resonances 26 , because our resonance lineshape depends on B 1 .…”

Section: Lettersmentioning

confidence: 96%

“…In the ultrastrong-coupling regime 2 , where B 1 ≈ B 0 , the spin-Dicke effect sets in 3 , which is equivalent in form to the familiar optical Dicke effect [5][6][7] . The driving field now defines the Bloch sphere axis, voiding the rotating-wave approximation 26 . In the Dicke regime, spins act together in phase with the driving field, leading to signatures of collective behaviour.…”

Section: Lettersmentioning

confidence: 99%

“…1b because the hyperfine-broadened resonance narrows 18,21 . Parallels to this RF effect exist in solution-based reaction-yield-detected magnetic resonance of pair processes [24][25][26] , with the crucial difference being that the OLED current reveals absolute population changes, allowing steady-state detection in magnetoresistance. This signal amplitude enables time-resolved excitation and detection to uncover spin-Rabi oscillations and spin beating due to correlated precession of electrons and holes 27 .…”

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confidence: 99%

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The spin-Dicke effect in OLED magnetoresistance

et al. 2015

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Pairs of charge-carrier spins in organic semiconductors constitute four-level systems that can be driven electromagnetically 1 . Given appropriate conditions for ultrastrong coupling 2 -weak local hyperfine fields B hyp , large magnetic resonant driving fields B 1 and low static fields B 0 that define Zeeman splittingthe spin-Dicke e ect, a collective transition of spin states, has been predicted 3 . This parameter range is challenging to probe by electron paramagnetic resonance spectroscopy because thermal magnetic polarization is negligible. It is accessed through spin-dependent conductivity that is controlled by electron-hole pairs of singlet and triplet spin-permutation symmetry without the need of thermal spin polarization 4 . Signatures of collective behaviour of carrier spins are revealed in the steady-state magnetoresistance of organic light-emitting diodes (OLEDs), rather than through radiative transitions. For intermediate B 1 , the a.c.-Zeeman e ect appears. For large B 1 , a collective spin-ensemble state arises, inverting the current change under resonance and removing power broadening, thereby o ering a unique window to ambient macroscopic quantum coherence.Macroscopic phase coherence is a hallmark of many exotic states of matter such as superconductivity, ferromagnetism or BoseEinstein condensation. Such coherence may also emerge between two-level systems, where it is mediated by electromagnetic fields, as described by the Dicke effect in collisional narrowing 5 and superradiance 6 . Collective behaviour may already arise within a pair of interacting two-level systems 7 , an observation that can potentially be extended to the prototypical two-level system of an electron spin. For pairs of charge-carrier spins in organic semiconductors, with driving fields B 1 exceeding the hydrogen-induced random local hyperfine field 1 B hyp and approaching the magnitude of the static magnetic field B 0 , a collective macroscopic spin phase has been predicted to emerge 3 . Under these conditions, when the spin-Rabi splitting becomes comparable to the Zeeman splitting, the electromagnetic field links individually resonant spin pairs together, forming a spin-Dicke state analogous to that in the dipolar Dicke effect [5][6][7] . These macroscopic effects are observable through measurements of electronic recombination rates, which depend on spin-permutation symmetry of the pair 8 .We monitor the electron-hole recombination current in an OLED, where positive and negative charges are injected into a thin film of an organic semiconductor from opposite electrodes. As the charges drift through the material, they can capture each other on intermolecular length scales owing to weak dielectric screening. These weakly coupled intermolecular electron-hole pairs 9 can ultimately recombine on individual molecules to form a molecular excited state, or exciton, which gives rise to electroluminescence. The subsequent discussion focuses on carrier pairs and not on excitons, which have spin S = 0 or 1. Because the carriers possess spi...

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“…The difference of θfunctions in Eq. (32) guarantees that in the time interval (0, T ) the field b z changes its sign exactly n times, so that n k=1 t k < T < n+1 k=1 t k . Taking the integral over t n+1 by parts leads to…”

Section: Appendixmentioning

confidence: 99%

Two-photon absorption in a two-level system enabled by noise

Mkhitaryan¹,

Boehme²,

Lupton³

et al. 2019

Phys. Rev. B

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We address the textbook problem of dynamics of a spin placed in a dc magnetic field and subjected to an ac drive. If the drive is polarized in the plane perpendicular to the dc field, the drive photons are resonantly absorbed when the spacing between the Zeeman levels is close to the photon energy. This is the only resonance when the drive is circularly polarized. For linearly polarized drive, additional resonances corresponding to absorption of three, five, and multiple odd numbers of photons is possible. Interaction with the environment causes the broadening of the absorption lines. We demonstrate that the interaction with environment enables the forbidden two-photon absorption. We adopt a model of the environment in the form of random telegraph noise produced by a single fluctuator. As a result of the synchronous time fluctuations of different components of the random field, the shape of the two-photon absorption line is non-Lorentzian and depends dramatically on the drive amplitude. This shape is a monotonic curve at strong drive, while, at weak drive, it develops a two-peak structure reminiscent of an induced transparency on resonance.

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

Cited by 13 publications

References 29 publications

Spin Biochemistry Modulates Reactive Oxygen Species (ROS) Production by Radio Frequency Magnetic Fields

Spin Biochemistry Modulates Reactive Oxygen Species (ROS) Production by Radio Frequency Magnetic Fields

The spin-Dicke effect in OLED magnetoresistance

Two-photon absorption in a two-level system enabled by noise

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