The mechanism of microwave-induced optical nuclear polarization in fluorene doped with phenanthrene: A qualitative analysis

Kesteren, H.W. van; Wenckebach, W.Th.; Schmidt, Jan

doi:10.1016/0009-2614(85)87210-9

Cited by 10 publications

(4 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The explanation by Kisselev [51] relies on changes of microwave propagation in the sample due to interaction of the microwaves with the electron spin resonance. However, primarily because our sample is only 3 mm thick, rather than 50 cm as in Kisselev’s experiments, we expect this effect to be negligible in our experiments; (2) In studies of microwave-induced optical nuclear spin polarization in molecular crystals by Schmidt, Wenkebach, and coworkers, the effect of both field and frequency modulation was studied at 0.3 T and 2.7 T over the 1.2–1.4 K temperature range [53–55]. By applying simultaneous in-phase field and frequency modulation, Wenckebach et al .…”

Section: Discussionmentioning

confidence: 99%

Low-temperature dynamic nuclear polarization at 9.4 T with a 30 mW microwave source

Thurber

Yau

Tycko

2010

Journal of Magnetic Resonance

167

191

View full text Add to dashboard Cite

Dynamic nuclear polarization (DNP) can provide large signal enhancements in nuclear magnetic resonance (NMR) by transfer of polarization from electron spins to nuclear spins. We discuss several aspects of DNP experiments at 9.4 Tesla (400 MHz resonant frequency for 1 H, 264 GHz for electron spins in organic radicals) in the 7-80 K temperature range, using a 30 mW, frequency-tunable microwave source and a quasi-optical microwave bridge for polarization control and low-loss microwave transmission. In experiments on frozen glycerol/water doped with nitroxide radicals, DNP signal enhancements up to a factor of 80 are observed (relative to 1 H NMR signals with thermal equilibrium spin polarization). The largest sensitivity enhancements are observed with a new triradical dopant, DOTOPA-TEMPO. Field modulation with a 10 G root-mean-squared amplitude during DNP increases the nuclear spin polarizations by up to 135%. Dependencies of 1 H NMR signal amplitudes, nuclear spin relaxation times, and DNP build-up times on the dopant and its concentration, temperature, microwave power, and modulation frequency are reported and discussed. The benefits of low-temperature DNP can be dramatic: the 1 H spin polarization is increased approximately 1000-fold at 7 K with DNP, relative to thermal polarization at 80 K.

show abstract

Section: Discussionmentioning

confidence: 99%

Low-temperature dynamic nuclear polarization at 9.4 T with a 30 mW microwave source

Thurber

Yau

Tycko

2010

Journal of Magnetic Resonance

167

191

View full text Add to dashboard Cite

show abstract

“…In these cases ESR hole-burning occurs and DNP is limited by the phonon-bottleneck. In materials in which n uclear cooling by thermal mixing is the dominant mechanism for DNP, such as the glassy materials used in the SMC experiments, FM is not expected to have a substantial eect [70]. The reason is that the whole ESR line is aected in the DNP due to spin-spin interactions.…”

Section: Polarization Enhancement By Frequency Modulationmentioning

confidence: 99%

The polarized double cell target of the SMC

Adams

Adeva

Arık

et al. 1999

Nuclear Instruments and Methods in Physics Research Section A:

View full text Add to dashboard Cite

The polarized target of the Spin Muon Collaboration at CERN was used for deep inelastic muon scattering experiments during 1993 to 1996 with a polarized muon beam to investigate the spin structure of the nucleon. Most of the experiments were carried out with longitudinal target polarization and 190 GeV muons, and some were done with transverse polarization and 100 GeV muons. Protons as well as deuterons were polarized by dynamic nuclear polarization DNP in three kinds of solid materials butanol, ammonia, and deuterated butanol, with maximum degrees of polarization of 94, 91, and 60 , respectively. Considerable attention was paid to the accuracies of the NMR polarization measurements and their analyses. The achieved accuracies were between 2.0 and 3.2 . The SMC target system with two cells of opposite polarizations, each cell 65 cm long and 5 cm in diameter, constitutes the largest polarized target system ever built and facilitates accurate spin asymmetry measurements. The design considerations, the construction and its performance over the years are reviewed.To be submitted to NIM A D.

show abstract

“…For materials in which the solid effect [9,10] dominates as a mechanism for DNP, it has been found that microwave FM can improve the rate of DNP. This appears to result from the fact that FM counteracts the effect of "hole burning" due to EPR absorption at a fixed frequency [11]. In the glassy alcohol materials with Cr(V) complexes, where the dynamic nuclear cooling [12] is the dominant mechanism for DNP, hole burning is not expected.…”

mentioning

confidence: 98%