CIDNP in a double switched magnetic field

Makarov, T. N.; Bagryanskaya, Elena G.; Shakirov, S. R.; Lukzen, Nikita N.; Sagdeev, R. Z.

doi:10.1016/s0009-2614(99)01385-8

Cited by 8 publications

(4 citation statements)

References 19 publications

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“…The MFEs manifest as non-equilibrium polarizations of the nuclear spins in the diamagnetic reaction products, producing enhanced or inverted NMR lines. This technique is known as "switched external magnetic field chemically induced dynamic nuclear polarization" (SEMF-CIDNP) [68,69].…”

Section: Solution-phase Experimentsmentioning

confidence: 99%

Magnetic field effects in chemical systems

Rodgers

2009

Pure and Applied Chemistry

178

205

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Chemical reactions that involve radical intermediates can be influenced by magnetic fields, which act to alter their rate, yield, or product distribution. These effects have been studied extensively in liquids, solids, and constrained media such as micelles. They may be interpreted using the radical pair mechanism (RPM). Such effects are central to the field of spin chemistry of which there have been several detailed and extensive reviews. This review instead presents an introductory account of the field of spin chemistry, suitable for use by graduate students or researchers who are new to the area. It proceeds by giving a brief historical overview of the development of spin chemistry, before introducing the essential theory. This is then illustrated by application to a series of recent developments in solution-phase magnetic field effects (MFEs). The closing pages of this review describe the role played by spin chemistry in the remarkable magnetic compass sense of birds and other animals.

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Section: Solution-phase Experimentsmentioning

confidence: 99%

Magnetic field effects in chemical systems

Rodgers

2009

Pure and Applied Chemistry

178

205

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“…The amplitude, the frequency and the phase of oscillations depend on the structure and occupancy of the spin levels in the short-lived intermediate species. The method described above was first implemented by Makarov et al 148 in relation to the photolysis of p-benzoquinone with 2-propanol-d 8 and to sensitised photoisomerisation of fumaronitrile. The oscillations of the CIDNP of the reaction products were recorded as functions of the delay t between the magnetic field switchings (Fig.…”

Section: Polarisation Under Conditions Of Double Switching Of the Ext...mentioning

confidence: 99%

Dynamic and stimulated nuclear polarisation in photochemical radical reactions

Bagryanskaya¹,

Sagdeev²

2000

Russ. Chem. Rev.

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“…(3)) in the framework of Redfield´s theory taking into account expressions (12). The correlation time can be estimated using the Debye relationship τ c = (4πr 3 η)/(3kT ), (14) where τ c is the rotational correlation time of a spherical particle of radius r in isotropic liquid of viscosity η at temperature T. The elements of the matrix, R d ij,kl , of HFI induced relaxation are calculated using relation (4). The structure of the matrix and the expressions for calculating its elements at (ω i τ c ) 2 << 1, where ω i denotes all pos sible energy splittings between the intrinsic energy levels, are presented in Ref.…”

Section: Spin Relaxation Due To Modulation Of Anisotropic Hyperfine Imentioning

confidence: 99%

Electron spin relaxation of radicals in weak magnetic fields

et al. 2006

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The review summarizes the results of studies on specific features of spin relaxation of radicals in liquids in weak magnetic fields.Key words: electron spin relaxation, weak magnetic field, free radicals, electron paramag netic resonance, spin polarization, chemically induced dynamic electron polarization.Many photochemical reactions involve radical stages. The interaction of external constant and alternating mag netic fields with electron and nuclear spins of intermedi ate radicals is the reason for the magnetic field and spin effects in radical chemical reactions. One of the key pa rameters determining the magnitude of the magnetic field effects is the spin relaxation rate of the intermediate radi cals. 1,2 In the case of long lived radical pairs (RPs), e.g., RPs in micellar solutions, 2 radical ion pairs, 3 biradicals, 4 etc., the spin relaxation is one of the main processes de termining the probability of RP recombination. The spin relaxation rate is an important parameter used in calcula tions of the magnetic field effect, 2 EPR spectra, 5 kinetics of chemically induced dynamic electron polarization (CIDEP), 1,6 optically detected EPR spectra, 3 stimulated nuclear polarization (SNP) spectra and kinetics, 7 etc. Usu ally, the magnetic field effects and the CIDEP, SNP, and optically detected EPR spectra are calculated assuming additive contributions of (i) electron relaxation in indi vidual radicals due to the interaction between an electron in a given radical and surrounding nuclei (modulation of anisotropic or isotropic HFI constant) or with the angular momentum of this radical (spin rotational relaxation) and (ii) dipole dipole and exchange relaxations due to the interaction between electrons in the radicals within the RP. Methods for the description of electron relaxation in the interacting radicals are not available as yet.To date, the electron spin dynamics and relaxation of free radicals have been well studied in strong magnetic fields that much exceed typical HFI constants of organic radicals. Various experimental techniques were elaborated and detailed theoretical concepts were proposed, which makes it possible to determine the spin relaxation rates by analyzing experimental data. 8, 9 Recently, there has been increasing literature on the behavior of radicals in weak magnetic fields whose magnitude is at most equal to the HFI constants of the radicals. Spin relaxation in weak magnetic fields has long been poorly studied both experi mentally and theoretically. Experimental studies are scarce because of relatively small number of methods of measur ing the relaxation times of radicals in weak magnetic fields. L Band time resolved EPR investigations of the radicals characterized by high HFI constants (30-70 mT) allow one to obtain information on the spin relaxation of radi cals in weak and zero magnetic fields. 10,11 Because the sensitivity of c.w. EPR in weak magnetic fields is low (~10 15 spins per sample), in this case information on elec tron spin relaxation can be extracted using indirect mag netic r...

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CIDNP in a double switched magnetic field

Cited by 8 publications

References 19 publications

Magnetic field effects in chemical systems

Magnetic field effects in chemical systems

Dynamic and stimulated nuclear polarisation in photochemical radical reactions

Electron spin relaxation of radicals in weak magnetic fields

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