نتایج جستجو برای: quadrupolar nuclei
تعداد نتایج: 62901 فیلتر نتایج به سال:
The solid-state NMR spectra of many NMR active elements are often extremely broad due to the presence of chemical shift anisotropy (CSA) and/or the quadrupolar interaction (for nuclei with spin I > 1/2). These NMR interactions often give rise to wideline solid-state NMR spectra which can span hundreds of kHz or several MHz. Here we demonstrate that by using fast MAS, proton detection and dipola...
Recentemente descrevemos um nova técnica capaz de obter espectros de RMN de alta resolução de núcleos quadrupolares com spins múltiplos de 1/2 no estado sólido, baseada no uso combinado de rotação no ângulo mágico (MAS) e espectroscopia múltipla quântica (MQ). Esta revisão descreve aspectos da teoria básica que suporta o experimento de RMN MQMAS de alta resolução e também enfatiza aspectos prát...
This article presents the realization of many self-reversible quantum logic gates using two-qubit quadrupolar spin 3/2 systems. Such operations are theoretically described using propagation matrices for the RF pulses that include the effect of the quadrupolar evolution during the pulses. Experimental demonstrations are performed using a generalized form of the recently developed method for quan...
An approach for enhancing the NMR sensitivity of the central transition of spin-3r2 nuclei is presented. Through selective excitation of the satellite transitions using a fast 1808 phase alternating pulse train during magic-angle spinning a < : selectively excited state is prepared where the populations of all eigenstates m with the same sign of m are equal, resulting in an enhanced central msy...
Rotor-assisted population transfer (RAPT) was developed as a method for enhancing MAS NMR sensitivity of quadrupolar nuclei by transferring polarization associated with satellite transitions to the central m=12-->-12 transition. After a single RAPT transfer, there still remains polarization in the satellite transitions that can be transferred to the central transition. This polarization is avai...
A novel approach to the determination of structure and potential dynamics in the solid-state NMR spectroscopy of half-integer quadrupolar nuclei is proposed and demonstrated. The new experiment combines into a single three-dimensional sequence, 2D multiple-quantum magic-angle-spinning NMR and 2D exchange NMR protocols. The result separates for each inequivalent chemical site its spin-diffusion ...
High-resolution solid state N M R spectroscopy of quadrupolar nuclei (preferentially n B and A1) has been employed to study the microstructure of glasses. Importance has been attached to the extraction of the fundamental N M R parameters like chemical shift, quadrupole coupling constant etc., from the spectra, first of all by applying satellite transition spectroscopy. Exemplary results are rep...
The surface of γ-alumina nanoparticles can be characterized by dynamic nuclear polarization (DNP) surface-enhanced NMR of (27)Al. DNP is combined with cross-polarization and MQ-MAS to determine local symmetries of (27)Al sites at the surface.
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