Multiple Echoes, Multiple Quantum Coherence, and the Dipolar Field: Demonstrating the Significance of Higher Order Terms in the Equilibrium Density Matrix

Minot, E.D.; Callaghan, Paul T.; Kaplan, N.

doi:10.1006/jmre.1999.1793

Cited by 33 publications

(31 citation statements)

References 9 publications

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“…To explain the multi-quantum coherence experiments two assumptions have to be revised: the high temperature approximation and the rule of the dipolar field (11,(13)(14)(15)17).…”

Section: Matrix Density Evolution In Crazed-like Experimentsmentioning

confidence: 99%

“…The second RF pulse transfers a part of these n-quantum coherences into m-spin one quantum terms (anti-phase magnetization). Finally, the magnetization can be rendered observable by a number of small intermolecular dipolar couplings that leave one-spin one-quantum coherence terms (in phase magnetization) to be detected (11,17). Gradient pulses, in the ratio 1:(ϩn) are applied to select the (ϩn)-quantum coherences and to discard other coherences.…”

Section: Theorymentioning

confidence: 99%

“…In a quantum-mechanical density operator treatment, without the high temperature approximation, when a CRAZED pulse sequence is applied to a liquid system, characterized by spin quantum number I ϭ 1/ 2, the first 90°pulse transforms the higher order terms of the density operator into intermolecular multi-quantum coherences (6,(11)(12)(13)(14)(15)(16)(17).…”

Section: Theorymentioning

confidence: 99%

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About the CRAZED sequence

Branca

Capuani

Maraviglia

2004

Concepts Magnetic Resonance

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ABSTRACT:In this article we report a detailed and understandable analysis of the evolution of various coherence orders in a Correlated 2D spectroscopy Revamped by Asymmetric Z-gradient Echo Detection (CRAZED) like pulse sequence, used to select a signal from intermolecular Multi Quantum Coherences (iMQCs). Because the signal tonoise-ratio of iMQC is much lower than the signal from conventional single quantum coherence (SQC), an optimization of experimental parameters is a necessity when measurements are made with iMQC. For this purpose a phase cycle is shown that not only allows a simpler selection of a particular quantum coherence order, but also removes receiver artifacts.

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“…To explain the multi-quantum coherence experiments two assumptions have to be revised: the high temperature approximation and the rule of the dipolar field (11,(13)(14)(15)17).…”

Section: Matrix Density Evolution In Crazed-like Experimentsmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

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About the CRAZED sequence

Branca

Capuani

Maraviglia

2004

Concepts Magnetic Resonance

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“…24 The Hahn echo originates from single-spin terms in the initial density operator; the nth DDF-induced echo originates from |n|-spin terms in the initial density operator [308]. This point will be discussed further in the next section.…”

Section: The Distant Dipolar Field 393mentioning

confidence: 99%

“…[76] and elsewhere [75,306,77,307]. The multiple-echo DDF effects in homonuclear spin systems have since been explained in terms of the quantum formalism, where the nth echo arises due to n-spin terms in the full equilibrium density operator [308]. There have been many subsequent studies of CRAZED-type sequences and the nature, excitation, and dynamics of iMQCs in solution NMR, e.g.…”

Section: Densitymentioning

confidence: 99%

Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects

Urban

2004

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Experimental and theoretical research conducted in two areas in the field of nuclear magnetic resonance (NMR) spectroscopy is presented: (1) studies of the coherent quantummechanical control of the angular momentum dynamics of quadrupolar (spin I > 1/2) nuclei and its application to the determination of molecular structure; and (2) applications of the long-range nuclear dipolar field to novel NMR detection methodologies.The dissertation is organized into six chapters. The first two chapters and associated appendices are intended to be pedagogical and include an introduction to the quantum mechanical theory of pulsed NMR spectroscopy and the time dependent theory of quantum mechanics.The third chapter describes investigations of the solid-state multiple-quantum magic angle spinning (MQMAS) NMR experiment applied to I = 5/2 quadrupolar nu-2 clei. This work reports the use of rotary resonance-matched radiofrequency irradiation for sensitivity enhancement of the I = 5/2 MQMAS experiment. These experiments exhibited certain selective line narrowing effects which were investigated theoretically.The fourth chapter extends the discussion of multiple quantum spectroscopy of quadrupolar nuclei to a mostly theoretical study of the feasibility of enhancing the resolution of nitrogen-14 NMR of large biomolecules in solution via double-quantum spectroscopy.The fifth chapter continues to extend the principles of multiple quantum NMR spectroscopy of quadrupolar nuclei to make analogies between experiments in NMR/nuclear quadrupolar resonance (NQR) and experiments in atomic/molecular optics (AMO). These analogies are made through the Hamiltonian and density operator formalism of angular momentum dynamics in the presence of electric and magnetic fields.The sixth chapter investigates the use of the macroscopic nuclear dipolar field to encode the NMR spectrum of an analyte nucleus indirectly in the magnetization of a sensor nucleus. This technique could potentially serve as an encoding module for the recently developed NMR remote detection experiment. The feasibility of using hyperpolarized xenon-129 gas as a sensor is discussed. This work also reports the use of an optical atomic magnetometer to detect the nuclear magnetization of Xe-129 gas, which has potential applicability as a detection module for NMR remote detection experiments.

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Intermolecular multiple quantum coherences in liquids

Richter

Warren

2000

Concepts Magn. Reson.

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In the early 1990s, the traditional framework of NMR spectroscopy was challenged through a series of simple experiments. The pulse sequences used consisted of a few RF pulses and a few gradient pulses, and the samples were mixtures of simple molecules. The spectra showed unexpected cross peaks between spins in different molecules.( ) In order to explain these results, two basic assumptions had to be revisited: 1 the ( ) high-temperature approximation to the Boltzmann distribution at equilibrium, and 2 the cancellation of dipolar couplings in solution. A close look at the physics involved showed that correlations between spins in separate molecules exist even after a single pulse, and that dipolar couplings can make these correlations visible in the presence of gradient pulses. A comprehensive description of the effect is given here, and some present and future applications are discussed.

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Multiple Echoes, Multiple Quantum Coherence, and the Dipolar Field: Demonstrating the Significance of Higher Order Terms in the Equilibrium Density Matrix

Cited by 33 publications

References 9 publications

About the CRAZED sequence

About the CRAZED sequence

Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects

Intermolecular multiple quantum coherences in liquids

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