Magnetic-field effect

Assuming reaction can only proceed via the singlet channel (to form a stable product) and for the radical pair to be in a singlet state, the magnetic field dependence on product yield can be summarised as follows  

Ag mechanism (assuming 7 = 0 T, Ag / 0 and Oi = aj = 0 T). At zero field there is no 5 — 7o, i mixing, however, as the field increases S — To mixing can occur. Hence with increasing field the rate of 5 - To also increases which reduces the product yield. 

Hyperfine coupling mechanism (HFCM) (assuming J = OF, Ag = 0 and a, and/or aj 0 T). At zero field the 5 mixes with ro, i) states, but as the field is increased 5 — r i mixing is suppressed due to the Zeeman interaction. This leads to a decrease in the rate of 5 — 7 i mixing with increasing field, which increases the product yield. 

HFCM and Ag mechanism (assuming J = OT, Ag 0 and a, and/or aj O T). This is the effect on the product yield when both the Ag and hyperfine mechanisms operate simultaneously. At low fields, the MFE is dominated by the hyperfine mechanism, but as the field strength increases the Ag mechanism starts to dominate. This has the effect of first increasing the product yield at lower fields and then reducing the yield with increasing Bo- 

MFE can be observed experimentally through measuring reaction yields, isotopic substitution or through the phenomena known as quantum beats [52, 53], with most observations being successfully explained through the radical pair mechanism. 

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M. Mihelcic, K. Wingerath. Threedimensional simulations of the Czochralski bulk flow in a stationary transverse magnetic field and in a vertical magnetic field Effects on the asymmetry of the flow and temperature distribution in the Si-melt. J Cryst Growth S2 318, 1987. 

The field, of strength E, is assumed in the z-direction the charge of the electron is e no magnetic field effects are considered, since the electron velocities are assumed small compared with the velocity of light.26 The Boltzmann equation is thus... 

Magnetic field effects on the reaction kinetics or yields of photochemical reactions in the condensed phase have been studied [20-23]. They have proved powerful for verifying the mechanism of photochemical reactions including triplet states. Previously, we obtained photogenerated triplet biradicals of donor-acceptor linked compounds, and found that the lifetimes of the biradicals were remarkably extended in the presence of magnetic fields up to 1T [24]. It has been reported that Cgo and its derivatives form optically transparent microscopic clusters in mixed solvents [25,26]. The clustering behavior of fullerene (C o) is mainly associated with the strong three-dimensional hydrophobic interactions between the C o units. Photoinduced... 

Magnetic field effects on the photoelectrochemical reactions of photosensitive electrodes are very important for practical applications of the MFEs in controlling the photoelectronic functions of molecular devices. Previously, we have examined MFEs on the photoelectrochemical reactions of photosensitive electrodes modified with zinc-tetraphenylporphyrin-viologen linked compounds [27, 28] and semiconductor nanoparticles [29, 30[. However, MEEs on the photoelectrochemical reactions of photosensitive electrodes modified with nanoclusters have not yet been reported. 

Semiconductor nanoparticles have been intensively studied because of their properties of quantum size effects [54]. A number of synthetic techniques have been reported and their characteristics have been studied by various spectroscopic methods [55, 56]. However, magnetic field effects (MFEs) on the photoelectrochemical properties of semiconductor nanocrystals had not until now been reported. 

As a reference, magnetic processing in the preparation of monolayer films consisting of Q-ZnS without Mn ion was also carried out. The luminescence at 400 nm was observed in the monolayer films, however, no magnetic field effects on the p-values for the monolayer films were observed. 

Magnetic Field Effects on the Dynamics of the Radical Pair in a Cgo Clusters-Phenothiazine System... 

Magnetic Field Effects on Photoelectrochemical Reactions of Electrodes Modified with the Ceo Nanocluster-Phenothiazine System... 

Yamaguchi, M. (2006) Magneto-Science Magnetic Field Effects on Materials Fundamentals and Applications (eds M. Yamaguchi and Y. Tanimoto), Kodansha-Springer, Chapter 1.1. 

Mogi, 1., Kamiko, M. and Okubo, S. (1995) Magnetic field effects on fractal morphology in electrochemical deposition. Physica B, 211, 319—322. 

Mogi, I. (1996) Magnetic field effects on the dopant-exchange process in polypyrrole. Bull. Chem. Soc. Jpn., 69, 2661—2666. 

Steiner, U. E. and Ulrich, T. (1989) Magnetic field effects in chemical kinetics and related phenomena. Chem. Rev., 89, 51-147. 

Nakagaki, R., Tanimoto, Y. and Mutai, K. (1993) Magnetic field effects upon photochemistry of bifuctional chain molecules./. Phys. Org. Chem., 6, 381-392. 

Magnetic field effects on photoelectrochemical responses of modified electrodes with porphyrin-viologen linked compound as a Langmuir-Blodgett film. Chem. Lett., 661—662. 

Yonemura, H Yoshida, M Mitake, S. and Yamada, S. (1999) Magnetic field effects on photocurrent responses from modified electrodes with CdS nanopartides. Electrochemistry, 67, 1209-1210. 

Yonemura, H., Kuroda, N., Moribe, S. and Yamada, S. (2006) Photoindiced electron-transfer and magnetic field effects on the dynamics of the radical pair in a Cgo clusters-phenofhiazine system. C. R, Chim., 9, 254-260. 

Haidar, M Misra, A., Banerjee, A. K. and Chowdhury, M. (1999) Magnetic field effect on the micellar (C)-pyrene- radical-pair system. J. Photochem. Photobiol. A, 127, 7-12. 

It was discovered by Al shits et al. (1987) that static magnetic fields of order 0.5T affect the motion of dislocations in NaCl crystals. This is not an intrinsic effect but is associated with impurities and/or radiation induced localized defects. Also, magnetic field effects have been observed in semiconductor crystals such as Si (Ossipyan et al., 2004). 

Figure 1.1 Effect of interelectronic repulsion, spin-orbit coupling and magnetic field on the energy levels arising from a given 4fn configuration for a free-ion Ln3+. The magnetic field effect is estimated assuming a 1 T field.

Figure 1.2 Energetic structure of a Kramers lanthanide ion in a ligand field evidencing the effect of progressively weaker perturbation. The magnetic field effect is estimated assuming a 1T field.

Mechanistic details of the microwave-induced oligomerization of methane on a microporous Mn02 catalyst were studied by Suib et al. [67], with emphasis on fundamental aspects such as reactor configuration, additives (chain propagators, dielectrics), temperature measurements, magnetic field effect, and reaction conditions. 

Little attention has been devoted to the effects of time-dependent magnetic fields (created by electromagnetic waves) in the absence of a strong magnetic field. Hore and his coworkers [123-125] recently described this effect as the oscillating magnetic field effect (OMFE) on the fluorescence of an exciplex formed in the photochemical reaction of anthracene with 1,3-dicyanobenzene over the frequency range 1-80 MHz. 

Fig. 14.13 The oscillating magnetic field effect (OMFE) in the triplet state radical pair reaction.

K. M. Salikhov.Y. N. Molin, R. Z. Sag-deev, A. L. Buchachenko, Spin Polarization and Magnetic Field Effects in Radical Reactions, Elsevier, Amsterdam, 1984. 

Isotope effects, magnetic, magnetic field effects and, on the products of organic reactions, 20, 1 Isotope effects, on nmr spectra of equilibrating systems, 23,63 Isotope effects, steric, experiments on the nature of, 10,1... 

Isotope effects, magnetic, magnetic field effects and, on the products of organic reactions,... 

The impact of Equation 10.14 in the treatment of spin-polarized systems is in two directions on the one hand, it allows the inclusion of external magnetic field effects in the description of /V-electron systems on the other hand, when the limit of zero magnetic field is imposed, the formalism becomes useful for /V-electron systems having spin-polarized ground state in the absence of a external magnetic field. This... 

Bhattacharyya K, Chowdhury M (1993) Environmental and magnetic field effects on exciplex and twisted charge transfer emission. Chem Rev 93 507-535... 

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