Applications of the parahydrogen phenomenon: A chemical perspective

Duckett, Simon B.; Sleigh, Christopher J.

doi:10.1016/s0079-6565(98)00027-2

Cited by 239 publications

(272 citation statements)

References 53 publications

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“…Extension of electron-nuclear and other high polarization transfer experiments involving noble gases, para-hydrogen, semiconductors, or photosynthetic reaction centers [11][12][13][14][15][16][17][18][19][20][21][22][23] to contemporary solid state and solution experiments is very appealing, since it could significantly enhance the sensitivity in a variety of NMR experiments. In particular, the theoretical enhancement for electron-nuclear polarization transfers is approximately ~(γ e /γ I ), where now the ratio is ~660, because of the large magnetic moment of the electron relative to the 1 H, making the gains in sensitivity large.…”

Section: Introductionmentioning

confidence: 99%

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

Bajaj

Hornstein

Kreischer

et al. 2007

Journal of Magnetic Resonance

158

126

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In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz 1 H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP-enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP-enhanced multidimensional NMR. These results include assignment of active site resonances in [U-13 C, 15 N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperaturedependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as low 12 mA) at frequencies between 320-365 GHz, suggesting an efficient route for the generation of even higher frequency radiation. The low starting currents were attributed to an elevated cavity Q, which is confirmed by cavity thermal load measurements. We conclude with an appendix containing a detailed description of the control system that safely automates all aspects of the gyrotron operation.

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Section: Introductionmentioning

confidence: 99%

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

Bajaj

Hornstein

Kreischer

et al. 2007

Journal of Magnetic Resonance

158

126

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“…The weak thermal polarization of nuclear spins has given NMR the reputation of being an inherently insensitive method. For example, even in magnetic fields of superconducting magnets, the polarization obtained does not exceed 10 −4 .A variety of available hyperpolarization techniques such as dynamic nuclear polarization (DNP), 8,9 chemically induced DNP (CIDNP), 1 0 spin-exchange optical pumping (SEOP) 11−13 of noble gases, and parahydrogen induced polarization (PHIP) [1][2][3]14,15 suggest that sensitivity limitations given by the Boltzmann thermal polarization can be overcome for a large range of analytes. All these hyperpolarization techniques, DNP, 16−19 CIDNP, 20−22 SEOP 23 and PHIP, 24,25 have been shown to greatly enhance sensitivity of low-field NMR experiments where thermal polarization is even lower.…”

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confidence: 99%

“…These experiments were performed with an identical 5 mm NMR tube. A sample of 250 μL neat (14 M) 15 N-labeled pyridine was polarized in a 1.6 T permanent magnet and then pneumatically shuttled to the zero-field region for detection. 35 The time for transfer of the sample from the magnet into the detection region was approximately 250 ms.…”

mentioning

confidence: 99%

Zero-Field NMR Enhanced by Parahydrogen in Reversible Exchange

et al. 2012

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ABSTRACT:We have recently demonstrated that sensitive and chemically specific NMR spectra can be recorded in the absence of a magnetic field using hydrogenative parahydrogen induced polarization (PHIP) 1−3 and detection with an optical atomic magnetometer. Here, we show that non-hydrogenative parahydrogen-induced polarization 4−6 (NH-PHIP) can also dramatically enhance the sensitivity of zero-field NMR. We demonstrate the detection of pyridine, at concentrations as low as 6 mM in a sample volume of 250 μL, with sufficient sensitivity to resolve all identifying spectral features, as supported by numerical simulations. Because the NH-PHIP mechanism is nonreactive, operates in situ, and eliminates the need for a prepolarizing magnet, its combination with optical atomic magnetometry will greatly broaden the analytical capabilities of zero-field and low-field NMR.T he past decade has witnessed increasing interest in the development of low-cost portable NMR spectrometers. 7 Such spectrometers promise to enable chemical analysis at greatly reduced cost in environments not accessible to standard high-field NMR technology. Detection of analytes at low concentrations primarily requires sensitive detectors and sufficient nuclear polarization. The weak thermal polarization of nuclear spins has given NMR the reputation of being an inherently insensitive method. For example, even in magnetic fields of superconducting magnets, the polarization obtained does not exceed 10 −4 .A variety of available hyperpolarization techniques such as dynamic nuclear polarization (DNP), 8,9 chemically induced DNP (CIDNP), 1 0 spin-exchange optical pumping (SEOP) 11−13 of noble gases, and parahydrogen induced polarization (PHIP) [1][2][3]14,15 suggest that sensitivity limitations given by the Boltzmann thermal polarization can be overcome for a large range of analytes. All these hyperpolarization techniques, DNP, 16−19 CIDNP, 20−22 SEOP 23 and PHIP, 24,25 have been shown to greatly enhance sensitivity of low-field NMR experiments where thermal polarization is even lower.Of equal importance, sensitive low-field NMR detectors of nuclear magnetization have been developed. These include systems based on inductive detectors, 7,26,27 superconducting quantum-interference devices (SQUIDs), 19,28−30 and optical magnetometers. 24,31−34 These technologies, in varying stages of maturity, permit the sensitive detection of low-frequency NMR signals, including NMR spectra in Earth's magnetic field.Combinations of hyperpolarization and novel detection schemes are thus particularly attractive in unconventional or portable NMR applications. For example, we have recently demonstrated that high-resolution and high SNR spectra can be recorded at zero field using PHIP from standard hydrogenative processes and an atomic magnetometer. 24 In the present contribution, we describe the first NMR experiments in zero field employing non-hydrogenative parahydrogen induced polarization (NH-PHIP) producing signal amplification by reversible exchange (SABRE). 4−6 Following the...

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“…We prepare pure spin states using an effect called parahydrogen induced polarization (PHIP) [17,18,19,20]. The existence of the para isomer of dihydrogen, H 2 , is a consequence of the Pauli principle, which requires the overall wavefunction to be antisymmetric with respect to exchange of the fermionic 1 H nuclei.…”

Section: Para-hydrogenmentioning

confidence: 99%

“…The para-hydrogen molecule cannot be used directly for NMR quantum computing, due to its high symmetry, but this can be overcome by using a chemical reaction to prepare a new molecule, in which the two hydrogen atoms can be made distinct and can be separately addressed. For further details see [12,13,14,15,17,18,19,20]. In our previous work we have used the two hydride 1 H nuclei in Ru(H) 2 (CO) 2 (dppe), where dppe indicates 1,2-bis(diphenylphosphino)ethane, as our NMR quantum computer.…”

Section: Para-hydrogenmentioning

confidence: 99%

Implementing Grover’s quantum search on a para-hydrogen based pure state NMR quantum computer

Anwar

Blazina

Carteret

et al. 2004

Chemical Physics Letters

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We demonstrate the implementation of Grover's quantum search algorithm on a liquid state nuclear magnetic resonance (NMR) quantum computer using essentially pure states. This was achieved using a two qubit device where the initial state is an essentially pure (ε = 1.06±0.04) singlet nuclear spin state of a pair of 1 H nuclei arising from a chemical reaction involving para-hydrogen. We have implemented Grover's search to find one of four inputs which satisfies a function.

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Applications of the parahydrogen phenomenon: A chemical perspective

Cited by 239 publications

References 53 publications

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

Zero-Field NMR Enhanced by Parahydrogen in Reversible Exchange

Implementing Grover’s quantum search on a para-hydrogen based pure state NMR quantum computer

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