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The continuous wave electron paramagnetic resonance experiment revisited

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dc.contributor.author Kälin M.
dc.contributor.author Gromov I.
dc.contributor.author Schweiger A.
dc.date.accessioned 2018-09-17T21:30:03Z
dc.date.available 2018-09-17T21:30:03Z
dc.date.issued 2003
dc.identifier.issn 1090-7807
dc.identifier.uri https://dspace.kpfu.ru/xmlui/handle/net/135071
dc.description.abstract When the modulation frequency used in continuous wave electron paramagnetic resonance (cw EPR) spectroscopy exceeds the linewidth, modulation sidebands appear in the spectrum. It is shown theoretically and experimentally that these sidebands are actually multiple photon transitions, σ++k × π, where one microwave (mw) σ+ photon is absorbed from the mw radiation field and an arbitrary number k of radio frequency (rf) π photons are absorbed from or emitted to the modulation rf field. Furthermore, it is demonstrated that both the derivative shape of the lines in standard cw EPR spectra and the distortions due to overmodulation are caused by the unresolved sideband pattern of these lines. The single-photon transition does not even give a contribution to the first-harmonic cw EPR signal. Multiple photon transitions are described semiclassically in a toggling frame and their existence is proven using second quantization. With the toggling frame approach and perturbation theory an effective Hamiltonian for an arbitrary sideband transition is derived. Based on the effective Hamiltonians an expression for the steady-state density operator in the singly rotating frame is derived, completely describing all sidebands in all modulation frequency harmonics of the cw EPR signal. The relative intensities of the sidebands are found to depend in a very sensitive way on the actual rf amplitude and the saturation of single sidebands is shown to depend strongly on the effective field amplitude of the multiple photon transitions. By comparison with the analogous solutions for frequency-modulation EPR it is shown that the field-modulation and the frequency-modulation technique are not equivalent. The experimental data fully verify the theoretical predictions with respect to intensities and lineshapes. © 2003 Elsevier Science (USA). All rights reserved.
dc.relation.ispartofseries Journal of Magnetic Resonance
dc.subject Electron paramagnetic resonance
dc.subject EPR
dc.subject ESR
dc.subject Modulation broadening
dc.subject Modulation sidebands
dc.subject Multiple photon transitions
dc.subject Toggling frame
dc.title The continuous wave electron paramagnetic resonance experiment revisited
dc.type Article
dc.relation.ispartofseries-issue 2
dc.relation.ispartofseries-volume 160
dc.collection Публикации сотрудников КФУ
dc.relation.startpage 166
dc.source.id SCOPUS10907807-2003-160-2-SID0042994218


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  • Публикации сотрудников КФУ Scopus [24551]
    Коллекция содержит публикации сотрудников Казанского федерального (до 2010 года Казанского государственного) университета, проиндексированные в БД Scopus, начиная с 1970г.

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