Radio frequency magnetic field effects on a radical recombination reaction: A diagnostic test for the radical pair mechanism

Journal of the American Chemical Society

Volumn 126, Issue 26, 2004, Pages 8102-8103

  Henbest, Kevin B ^a   Kukura, Philipp ^a   Rodgers, Christopher T ^a   Hore, P J ^a   Timmel, Christiane R ^a  

^a UNIVERSITY OF OXFORD   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; CHEMICAL REACTION; COMPUTER SIMULATION; DIAGNOSTIC TEST; ELECTRON TRANSPORT; MAGNETIC FIELD; MOLECULAR INTERACTION; OSCILLATION; RADIOFREQUENCY;

EID: 3042850008     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja048220q     Document Type: Article

References (18)

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5. It should be noted that since radical pairs typically have a lifetime < 1 μs, fields with frequencies < 1 kHz (periods > 1 ms) should have a very similar effect to a static field.
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11. Radical pairs were produced in a spin-correlated singlet state by UV continuous illumination. The linearly polarized RF field was 100% audio frequency amplitude-modulated, and the exciplex fluorescence was detected by a photomultiplier and lock-in amplifier. To this apparatus, described in detail elsewhere (Timmel, C. R.; Woodward, J. R.; Hore, P. J.; McLauchlan, K. A.; Stass, D. V. Meas. Sci. Technol. 2001, 12, 635-643), was added a pair of water-cooled Helmholtz coils to provide a static magnetic field of up to 4 mT, mounted to allow different relative orientations of the two fields. The strength of the static field was swept, maintaining a fixed frequency and strength for the RF field. The experiment measures the integral of the modulated fluorescence over a cycle of the audio frequency modulation. All experiments were performed at room temperature. The samples comprised 0.5 mM Chr and 10 mM DCB in a 9:1 cyclohexanol/acetonitrile mixture (by volume).
12. 0/2π, where γ is the gyromagnetic ratio of the electron.
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17. The following changes to the γ-COMPUTE algorithm were made: (a) the calculation took place in the laboratory frame of reference, (b) the periodicity of the spin Hamiltonian arose from the interaction with the RF field rather than the modulation of anisotropic magnetic interactions by sample spinning, (c) the integral over the powder angle γ became an average over the phase of the RF field at the moment of creation of the radical pair, and (d) instead of the NMR spectrum, we computed the singlet product yield using the "exponential model"8 for the radical recombination kinetics. Spectra were calculated as the difference between the yields with and without unmodulated RF irradiation. Simulations indicated that such spectra closely resembled the yield integrated over a cycle of the audio frequency modulation.
18. Ritz, T.; Thalau, P.; Phillips, J. B.; Wiltschko, R.; Wiltschko, W. Nature 2004, 429, 177-180.