Selectivity in multiple quantum nuclear magnetic resonance
The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.
- Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
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- Research Org:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
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- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Country of Publication:
- United States
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; NUCLEAR MAGNETIC RESONANCE; HAMILTONIANS; QUANTUM MECHANICS; BENZENE; COMPUTER CALCULATIONS; ENERGY-LEVEL TRANSITIONS; FOURIER TRANSFORMATION; MOLECULES; PULSE TECHNIQUES; SPIN; T INVARIANCE; ZEEMAN EFFECT; ANGULAR MOMENTUM; AROMATICS; HYDROCARBONS; INTEGRAL TRANSFORMATIONS; INVARIANCE PRINCIPLES; MAGNETIC RESONANCE; MATHEMATICAL OPERATORS; MECHANICS; ORGANIC COMPOUNDS; PARTICLE PROPERTIES; QUANTUM OPERATORS; RESONANCE; TRANSFORMATIONS 656000* -- Condensed Matter Physics
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