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J Phys Chem A. 2016 Nov 3;120(43):8657-8679. Epub 2016 Oct 25.

Controlling the Dynamics of Quadrupolar Spin-1 Nuclei by Means of Average Hamiltonian Theory When Irradiated with Modified Composite Quadrupolar Echo Pulse Sequences.

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The Graduate Center, Physics, The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States.
Department of Engineering, Physics, and Technology, The City University of New York, BCC , 2155 University Avenue, CPH 118, New York, New York 10453, United States.
Department of Applied Physics, New York University , 6 Metrotech Center, New York, New York 11201, United States.
Physics Department and Shanghai Key Laboratory of Magnetic Resonance, East China Normal University , Shanghai 20062, China.


The importance of the average Hamiltonian theory and its antecedent the Magnus expansion are discussed. The investigation of its convergence in different situations is very important. In this paper, we introduced a well-established approach to minimize the zeroth-order average Hamiltonian for modified composite pulse sequence in quadrupolar spectroscopy of spin-1. We designed two modified composite pulse sequences constructed by modifying the timing sequence in the original composite pulse sequences.17 We tested various configurations of times associated with the free evolution of the spin system in the modified composite pulses. We found that by decreasing the time delays between the pulses associated with the free evolution of spin system, the line shapes become increasingly better until we obtained the new modified composite pulses showing improvement of the signal compared to the original composite pulse sequences.17 This promising work is expected to play an important role not only for recording high resolution spectra of amino acids, pharmaceutical samples, and peptides but also for probing structural and dynamic information in biomolecules. The generality of the present theoretical scheme points to potential applications in solid-state NMR, to problems in chemical physics, quantum mechanics and theoretical developments, chemistry, and physical chemistry, and in interdisciplinary research areas whenever they include spin dynamics approach.

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