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Radical pair kinetics is determined by the coherent and incoherent spin dynamics of spin pair and spin-selective chemical reactions. In a previous paper, reaction control and nuclear spin state selection by designed radiofrequency (RF) magnetic resonance was proposed. Here, we present two novel types of reaction control calculated by the local optimization method. One is anisotropic reaction control and the other is coherent path control. In both cases, the weighting parameters for the target states play an important role in the optimizing of the RF field. In the anisotropic control of radical pairs, the weighting parameters play an important role in the selection of the sub-ensemble. In coherent control, one can set the parameters for the intermediate states, and it is possible to specify the path to reach a final state by adjusting the weighting parameters. The global optimization of the weighting parameters for coherent control has been studied. These manifest calculations show the possibility of controlling the chemical reactions of radical pair intermediates in different ways. [ABSTRACT FROM AUTHOR]

Recently, AWG (arbitrary waveform generator) based pulse electron paramagnetic resonance and nuclear magnetic resonance have been developed in a high field regime for the improvement of sensitivity and selectivity and quantum information processing. Here, we propose the application of AWG based reaction control of radical pairs in a rather low magnetic field regime. We calculated the locally optimized radio frequency (RF) field with the control theory by Sugawara [J. Chem. Phys. 118(15), 6784–6800 (2003)]. The calculation results manifest the applicability of AWG-RF fields to reaction control (reaction yield detected magnetic resonance), stimulated nuclear polarization, magnetic isotope selection, and coherent control of the spin dynamics. [ABSTRACT FROM AUTHOR]

Approximately 50 species, including birds, mammals, reptiles, amphibians, fish, crustaceans and insects, are known to use the Earth's magnetic field for orientation and navigation (1) Birds in particular have been [...]

A study is conducted of the spin mixing process of the radical pair in sodium dodecyl sulfate (SDS) micelle by using a novel technique nanosecond pulsed magnetic field effect on transient absorption. Coherent spin mixing process, incoherent spin mixing process and incoherent longitudinal spin mixing process are the three stages with the help of which the spin mixing process can be realized.

The kinetics of intermediates generated from intermolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule is studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part.

A study of the effect of short microwave pulse irradiation on the spin correlated radical pairs generated by the hydrogen abstraction reaction of triplet excited xanthone with tert-butyl-substituted phenols in a micellar dodecyl sulfate solution using time-resolved transient optical absorption technique is presented. The results show that analysis of the double frequency beats exhibits the spin dephasing process between the triplet states of the radical pair as the main cause of the double beats decay.

The photoinduced electron transfer reaction between the excited triplet state of xanthone and N,N-diethylaniline was examined using the recently developed photoconductivity detected magnetic resonance (PCDMR) method. For the first time, the PCDMR spectrum of the transient radical-ion pair formed by the photochemical reaction of xanthone/N,N-diethylaniline in 2-propanol is observed. Irradiation with strong microwaves revealed a peculiar PCDMR spectrum, which shows the spin-locking effect at the center and the pumping effect on both wing portions. The long lifetime of the radical-ion pairs causes this shape and is estimated to be 2 x 10(super -7) s at room temperature.

Spin-selective reactions of radical pairs are conventionally modelled using an approach that dates back to the 1970s [R. Haberkorn, Mol. Phys. 32, 1491 (1976)]. An alternative approach based on the theory of quantum measurements has recently been suggested [J. A. Jones and P. J. Hore, Chem. Phys. Lett. 488, 90 (2010)]. We present here the first experimental attempt to discriminate between the two models. Pulsed electron paramagnetic resonance spectroscopy has been used to investigate intramolecular electron transfer in the radical pair form of a carotenoid-porphyrinfullerene molecular triad. The rate of spin-spin relaxation of the fullerene radical in the triad was found to be inconsistent with the quantum measurement description of the spin-selective kinetics, and in accord with the conventional model when combined with spin-dephasing caused by rotational modulation of the anisotropic g-tensor of the fullerene radical. [ABSTRACT FROM AUTHOR]

In this work, we propose to extend the scope of single-molecule spectroscopy to spin chemistry investigations of single radical pairs. A consistent theory of single-molecule spectroscopy on single radical pairs is proposed, which allows one to show that bunching phenomena are affected by singlet–triplet interconversion in radical pairs, which is, in turn, affected by local and external magnetic fields. A detailed study on the feasibility of such experiments with single flavin adenine dinucleotide, FAD, molecules is presented. We conclude that the observation of magnetic field effects on single FAD molecules is feasible but experimentally challenging for measurements on integrated fluorescence intensity and fluorescence event statistics. [ABSTRACT FROM AUTHOR]

The effects of weak static magnetic fields (not exceeding 46 mT) on radical recombination reactions are employed to study the protein-substrate interactions. The experimental data showed that the triplet state of the radical pair [super T][[AQDS.sup.3-*] Trp*] (where AQDS = anthraquinone-2,6-disulfonate) produced by either hen egg white lysozyme (HEWL) or bovine serum albumin (BSA) have a lifetime of the order of microseconds in both systems (HEWL and BSA).

The stabilization of the radical cation of the cucurbituril-insulated oligoaniline rotaxane by a threaded cucurbituril macrocycle is discussed. The thermodynamic and kinetic stability of the cation can also be improved by the encapsulation of the compound.

The photoinduced electron transfer reactions of hen egg- white lysozyme (HEWL) and flavin dyes are studied. A large magnetic field effect (MFE) up to 13 percent of the yield of the free radical formation is found in the photoinduced electron transfer reaction from the tryptophan residue of HEWL to the flavin mononucleotide (FMN).