%0 Journal Article %J Journal of Magnetic Resonance %D 2005 %T NMR detection using laser-polarized xenon as a dipolar sensor %A Granwehr, J. %A Urban, J. T. %A Trabesinger, A. H. %A Pines, A. %K dynamics %X

Hyperpolarized Xe-129 can be used as a sensor to indirectly detect NMR spectra of heteronuclei that are neither covalently bound nor necessarily in direct contact with the Xe atoms, but coupled through long-range intermolecular dipole-dipole interactions. To reintroduce long-range dipolar couplings the sample symmetry has to be broken. This can be done either by using an asymmetric sample arrangement, or by breaking the symmetry of the spin magnetization with field gradient pulses. Experiments are performed where only a small fraction of the available Xe-129 magnetization is used for each point, so that a single batch of xenon suffices for the point-by-point acquisition of a heteronuclear NMR spectrum. Examples with H-1 as the analyte nucleus show that these methods have the potential to obtain spectra with a resolution that is high enough to determine homonuclear J couplings. The applicability of this technique with remote detection is discussed. Published by Elsevier Inc.

%B Journal of Magnetic Resonance %V 176 %P 125-139 %8 Oct %@ 1090-7807 %G English %U ://WOS:000232425800001 %N 2 %M WOS:000232425800001 %! NMR detection using laser-polarized xenon as a dipolar sensor %R Doi 10.1016/J.Jmr.2005.05.013 %0 Journal Article %J Physical Review Letters %D 2004 %T Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry %A Yashchuk, V. V. %A Granwehr, J. %A Kimball, D. F. %A Rochester, S. M. %A Trabesinger, A. H. %A Urban, J. T. %A Budker, D. %A Pines, A. %K mri %X

We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency-modulated light to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample (1.7 cm(3) at a pressure of 5 bars, natural isotopic abundance, polarization 1%), prepared remotely to the detection apparatus, is measured with an atomic sensor. An average magnetic field of similar to10 nG induced by the xenon sample on the 10 cm diameter atomic sensor is detected with signal-to-noise ratio similar to10, limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.

%B Physical Review Letters %V 93 %8 Oct 15 %@ 0031-9007 %G English %U ://WOS:000224533300012 %N 16 %M WOS:000224533300012 %! Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry %R Doi 10.1103/Physrevlett.93.160801 %0 Journal Article %J Solid State Nuclear Magnetic Resonance %D 2002 %T Investigations of low-amplitude radio frequency pulses at and away from rotary resonance conditions for I=5/2 Nuclei %A Logan, J. W. %A Urban, J. T. %A Walls, J. D. %A Lim, K. H. %A Jerschow, A. %A Pines, A. %K solid-state %X

Additional experimental evidence of rotary resonance effects for multiple-quantum coherence conversion in a spin-5/2 system is presented. Two-dimensional plots of the relative efficiency of MQ excitation and conversion are given as a function of radio frequency (rf) amplitude and pulse width. Data are presented for the excitation of five-quantum coherence (5QC), as well as for 5QC to three-quantum coherence (3QC) conversion, 5QC to 1QC (the central transition coherence) conversion, and 3QC to 1 QC conversion. A two-fold increase in the signal-to-noise ratio is achieved by substituting low amplitude rf pulses in place of hard rf pulses for 5QC excitation and 5QC to 3QC conversion in a mixed multiple-quantum magic angle spinning (MAS) (MMQMAS) experiment. The anisotropic line shape for the low-amplitude rf pulse version of the MMQMAS experiment was observed to be distorted from the MAS line shape. The cause and implications of the distortion are discussed. (C) 2002 Elsevier Science (USA).

%B Solid State Nuclear Magnetic Resonance %V 22 %P 97-109 %8 Sep-Nov %@ 0926-2040 %G English %U ://WOS:000179154400003 %N 2-3 %M WOS:000179154400003 %! Investigations of low-amplitude radio frequency pulses at and away from rotary resonance conditions for I=5/2 Nuclei %R Doi 10.1006/Snmr.2002.0084 %0 Journal Article %J Journal of Chemical Physics %D 2002 %T Theoretical investigations of I=5/2 quadrupolar spin dynamics in the sudden-passage regime %A Walls, J. D. %A Lim, K. H. %A Logan, J. W. %A Urban, J. T. %A Jerschow, A. %A Pines, A. %K SPECTROSCOPY %X

The theoretical approach utilizing bimodal Floquet theory in the quadrupolar/central-transition interaction frame, presented in an earlier article [J. D. Walls, K. H. Lim, and A. Pines, J. Chem. Phys. 116, 79 (2002)], is extended to describe the more complicated spin dynamics of I=5/2 spin systems. Rotary resonance effects occur when the strength of the radio-frequency irradiation, omega(1), matches the sample spinning speed, omega(r), at the conditions omega(1) = 2/3nomega(r) (n integral). At these conditions, conversions of both triple-quantum and five-quantum coherences to central-quantum coherence are observed. Between rotary resonance conditions [ 2n/3omega(r)<ω(1)<[2(n+1)]/3ω(r)], five-quantum as well as triple-quantum coherences can be created from equilibrium z-magnetization via a nutation mechanism. In addition, effective transfer between five-quantum and triple-quantum coherences also is observed in between rotary resonance conditions. These effects have been investigated theoretically and verified by both numerical calculations and experimental results. (C) 2002 American Institute of Physics.

%B Journal of Chemical Physics %V 117 %P 518-532 %8 Jul 8 %@ 0021-9606 %G English %U ://WOS:000176424800003 %N 2 %M WOS:000176424800003 %! Theoretical investigations of I=5/2 quadrupolar spin dynamics in the sudden-passage regime %R Doi 10.1063/1.1483256