Microwave-induced optical nuclear polarization (MI-ONP)

Deimling, M.; Brunner, H.; Dinse, Klaus−Peter; Hausser, Karl H.; Colpa, J.P.

doi:10.1016/0022-2364(80)90128-6

Cited by 27 publications

(26 citation statements)

References 16 publications

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“…33 An effect similar to the SE can be used to transfer polarization between an excited electronic triplet state and a nucleus via forbidden transitions. This mechanism is referred to as microwave induced optical nuclear polarization and was introduced by Deimling et al 34 Other polarization schemes rely on the use of 3 He ( Ref. 35 ) and quantum dots.…”

Section: Introduction/backgroundmentioning

confidence: 99%

Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

791

847

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Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (μw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (γ e /γ l ), being ∼660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (≥5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in μw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

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Section: Introduction/backgroundmentioning

confidence: 99%

Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

791

847

View full text Add to dashboard Cite

show abstract

“…Unfortunately, the paramagnetic centers necessary for DNP are often harmful for the subsequent application. This problem is overcome by the method of Microwave Induced Optical Polarization (MIONP) [2,3] where photoexcited paramagnetic states are used that disappear after being used for DNP.…”

Section: Introductionmentioning

confidence: 99%

Microwave Induced Optical Nuclear Polarization at 75 GHz: A quantitative analysis

1993

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A quantitative analysis of Microwave Induced Optical Nuclear Polarization (MIONP) on crystals of fluorene-h., doped with phenanthrene-d., at 75 GHz and 1.4 K is presented. Two effects are studied in detail: the nuclear spin diffusion barrier and the phonon bottleneck. Experiments are presented that allow the identification of the proton spins on fluorene-h., molecules located inside the nuclear spin diffusion barrier surrounding phenanthrene-d., molecules excited in the photo-excited triplet state. Using this result the experimental values for the triplet spin-lattice relaxation (SLR) rates and the nuclear SLR rate can be related to each other without any fitting parameter. Microwave frequency and magnetic field modulation are used during MIONP to prove that the triplet SLR is phonon-bottlenecked, Subsequently a quantitative analysis of MIONP in the system fluorene-h., doped with phenanthrene-d., is obtained.

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“…The coupling may be provided by a static hyper fine interaction in an· electron triplet level crossing (LC) region ( 3] , by electron spin-nuclear spin relaxation resulting from a time dependent hyper fine interaction I 4] , or by externally applied radio frequency fields tuned to "forbidden" electron spin-nuclear spin transitions (5,6]. A common feature of previous ONP experiment's is that the crystal under investigation is irradiated continuously with UV light in a constant magnetic f.ield until sufficient nuclear polarization develops to be detected by standard NMR techniques.…”

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confidence: 99%