@article {318, title = {NMR detection using laser-polarized xenon as a dipolar sensor}, journal = {Journal of Magnetic Resonance}, volume = {176}, year = {2005}, note = {J Magn Reson972AITimes Cited:14Cited References Count:46}, month = {Oct}, pages = {125-139}, abstract = {

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.

}, keywords = {dynamics}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2005.05.013}, url = {://WOS:000232425800001}, author = {Granwehr, J. and Urban, J. T. and Trabesinger, A. H. and Pines, A.} } @article {321, title = {Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry}, journal = {Physical Review Letters}, volume = {93}, year = {2004}, note = {Phys Rev Lett863ATTimes Cited:32Cited References Count:22}, month = {Oct 15}, abstract = {

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.

}, keywords = {mri}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.93.160801}, url = {://WOS:000224533300012}, author = {Yashchuk, V. V. and Granwehr, J. and Kimball, D. F. and Rochester, S. M. and Trabesinger, A. H. and Urban, J. T. and Budker, D. and Pines, A.} } @article {359, title = {Investigations of low-amplitude radio frequency pulses at and away from rotary resonance conditions for I=5/2 Nuclei}, journal = {Solid State Nuclear Magnetic Resonance}, volume = {22}, year = {2002}, note = {Solid State Nucl Mag613WLTimes Cited:8Cited References Count:40}, month = {Sep-Nov}, pages = {97-109}, abstract = {

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).

}, keywords = {solid-state}, isbn = {0926-2040}, doi = {Doi 10.1006/Snmr.2002.0084}, url = {://WOS:000179154400003}, author = {Logan, J. W. and Urban, J. T. and Walls, J. D. and Lim, K. H. and Jerschow, A. and Pines, A.} } @article {351, title = {Theoretical investigations of I=5/2 quadrupolar spin dynamics in the sudden-passage regime}, journal = {Journal of Chemical Physics}, volume = {117}, year = {2002}, note = {J Chem Phys566JRTimes Cited:3Cited References Count:44}, month = {Jul 8}, pages = {518-532}, abstract = {

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.

}, keywords = {SPECTROSCOPY}, isbn = {0021-9606}, doi = {Doi 10.1063/1.1483256}, url = {://WOS:000176424800003}, author = {Walls, J. D. and Lim, K. H. and Logan, J. W. and Urban, J. T. and Jerschow, A. and Pines, A.} }