Transfer of the Haupt-hyperpolarization to neighbor spins

Icker, Maik; Fricke, Pascal; Berger, Stefan

doi:10.1016/j.jmr.2012.07.019

Cited by 16 publications

(18 citation statements)

References 14 publications

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“…In this case the LLS is given by the imbalance in populations between spin states spanning different irreducible representations of the C 3 permutation group [32]. Some materials, such as γ-picoline, display quantum-rotor induced polarization (QRIP) effects, in which a large polarization of the methyl LLS is induced by dissolution of the material from cryogenic conditions [29,[33][34][35]. However, the hyperpolarized LLS only gives rise to observable NMR signals through an incoherent crossrelaxation mechanism involving a fourth nuclear spin, which greatly reduces the available signal enhancement [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Long-lived nuclear spin states in monodeuterated methyl groups

Elliott

Brown

Dumez

et al. 2016

Phys. Chem. Chem. Phys.

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It is possible to access long-lived nuclear singlet order in monodeuterated methyl groups, in the case that a significant chemical shift difference exists between the CH 2 D protons. This occurs when the local environment is chiral, and the CH 2 D rotamers have different populations. An experimental demonstration is presented for the case of N-CH 2 D-2-methylpiperidine. The ratio of the singlet relaxation time constant T S to the longitudinal relaxation time constant T 1 is found to be equal to 3.1 ± 0.1, over a wide range of temperatures, solvents, and magnetic fields. The longest observed value of T S approaches 1 minute. The relaxation mechanisms of the long-lived state are discussed, and a modified model of the CH 2 D geometry is proposed to explain the observed ratio of T S to T 1 .

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Section: Introductionmentioning

confidence: 99%

Long-lived nuclear spin states in monodeuterated methyl groups

Elliott

Brown

Dumez

et al. 2016

Phys. Chem. Chem. Phys.

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“…Electronic mail: a.horsewill@nottingham.ac.uk perature, Ludwig et al 5 observe hyperpolarization effects that compete with dynamic nuclear polarization. Similarly inducing a sudden rise in temperature in CH 3 containing samples, Icker et al 6,7 have reported anti-phase multiplet components in the high-resolution NMR spectrum of 13 C-γ -picoline. A theoretical framework successfully describing such quantum rotor-induced polarization has recently been presented by the group of Levitt in Southampton.…”

Section: Introductionmentioning

confidence: 92%

Spin-symmetry conversion in methyl rotors induced by tunnel resonance at low temperature

Zhang

Sun

Alsanoosi

et al. 2014

The Journal of Chemical Physics

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Field-cycling NMR in the solid state at low temperature (4.2 K) has been employed to measure the tunneling spectra of methyl (CH 3 ) rotors in phenylacetone and toluene. The phenomenon of tunnel resonance reveals anomalies in 1 H magnetization from which the following tunnel frequencies have been determined: phenylacetone, ν t = 6.58 ± 0.08 MHz; toluene, ν t(1) = 6.45 ± 0.06 GHz and ν t(2) = 7.07 ± 0.06 GHz. The tunnel frequencies in the two samples differ by three orders of magnitude, meaning different experimental approaches are required. In phenylacetone the magnetization anomalies are observed when the tunnel frequency matches one or two times the 1 H Larmor frequency. In toluene, doping with free radicals enables magnetization anomalies to be observed when the tunnel frequency is equal to the electron spin Larmor frequency. Cross-polarization processes between the tunneling and Zeeman systems are proposed and form the basis of a thermodynamic model to simulate the tunnel resonance spectra. These invoke space-spin interactions to drive the changes in nuclear spin-symmetry. The tunnel resonance lineshapes are explained, showing good quantitative agreement between experiment and simulations. © 2014 AIP Publishing LLC.

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“…Indeed, progress has been made in utilising the Haupt effect, a phenomenon that applies to weakly hindered CH 3 groups 12,13 , in nuclear polarisation schemes. Additionally, the group of Levitt has explained and exploited remarkable hyperpolarisation effects in solution NMR attributed to quantum rotor effects of CH 3 5, 14, 15 which were first observed by Icker and Berger 16,17 .…”

Section: Introductionmentioning

confidence: 99%

Manipulating and probing the polarisation of a methyl tunnelling system by field-cycling NMR

Zhang

Abu-Khumra

Aibout

et al. 2017

The Journal of Chemical Physics

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In NMR the polarisation of the Zeeman system may be routinely probed and manipulated by applying resonant rf pulses. As with spin-½ nuclei, at low temperature the quantum tunnelling states of a methyl rotor are characterised by two energy levels and it is interesting to consider how these tunnelling states might be probed and manipulated in an analogous way to nuclear spins in NMR. In this paper experimental procedures based on magnetic field-cycling NMR are described where, by irradiating methyl tunnelling sidebands, the polarisations of the methyl tunnelling systems are measured and manipulated in a prescribed fashion. At the heart of the technique is a phenomenon that is closely analogous to dynamic nuclear polarisation and the solid effect where forbidden transitions mediate polarisation transfer between 1 H Zeeman and methyl tunnelling systems. Depending on the irradiated sideband, both positive and negative polarisations of the tunnelling system are achieved, the latter corresponding to population inversion and negative tunnelling temperatures. The transition mechanics are investigated through a series of experiments and a theoretical model is presented that provides good quantitative agreement.

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Transfer of the Haupt-hyperpolarization to neighbor spins

Cited by 16 publications

References 14 publications

Long-lived nuclear spin states in monodeuterated methyl groups

Long-lived nuclear spin states in monodeuterated methyl groups

Spin-symmetry conversion in methyl rotors induced by tunnel resonance at low temperature

Manipulating and probing the polarisation of a methyl tunnelling system by field-cycling NMR

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