نتایج جستجو برای: quadrupolar nuclei
تعداد نتایج: 62901 فیلتر نتایج به سال:
This work focuses on analyzing the dynamics of spin I=1 nuclei evolving under a simple two pulse echo cycle and a magic echo cycle by average Hamiltonian theory. The work highlights how spectral artifacts introduced by finite pulse widths can be removed by cycling the phases of the receiver and transmitter in a well defined way. In addition, it is shown that a magic echo cycle can refocus both ...
The present work introduces a new three-dimensional nuclear magnetic resonance ~3D NMR! experiment for the analysis of half-integer quadrupolar nuclei in solids. The method is based on the multi-rank expansion of the high-field NMR Hamiltonian governing the central transition of these spins in terms of irreducible spherical tensor elements. This approach leads to a temporal spin evolution given...
We discuss the recoupling of homonuclear dipolar interactions between quadrupolar nuclei under magic-angle spinning conditions, caused by the first-order quadrupolar interaction. This recoupling leads to NMR linewidths displaying a nonmonotonic dependence on the spinning frequency, meaning that broader lines may result as the spinning rate is increased. The effect depends on geometrical paramet...
A new two-dimensional magic-angle spinning NMR experiment1,2 using multiple-quantum coherences of half-integer quadrupolar nuclei was used to study 27Al sites in crystalline samples of leucite (KAlSi2O6), anorthite (CaAl2Si2O8), and kyanite (Al2SiO5), as well as CaAl2Si2O8 glass and a magnesium aluminoborate glass. In the crystals, multiple sites are partially resolved and new results for isotr...
In this contribution, we extend the theory of symmetry-based pulse sequences of types CN(n) (nu) and RN(n) (nu) in magic-angle-spinning nuclear resonance spectroscopy [M. H. Levitt, in Encyclopedia of Nuclear Magnetic Resonance, edited by D. M. Grant and R. K. Harris (Wiley, Chichester, 2002), Vol. 9]. to the case of rotating the sample simultaneously around two different angles with respect to...
New multidimensional NMR methods correlating the quadrupolar and heteronuclear dipolar interactions affecting a half-integer quadrupolar spin in the solid state are introduced and exemplified. The methods extend separated-local-field magic-angle spinning (SLF MAS) NMR techniques that have been used successfully in spin-(1)/(2) spectroscopy to the study of S >/= (3)/(2) nuclei. In our implementa...
Nuclear magnetic resonance is viewed as an important technique for the implementation of many quantum information algorithms and protocols. Although the most straightforward approach is to use the two-level system composed of spin 1/2 nuclei as qubits, quadrupolar nuclei, which possess a spin greater than 1/2, are being used as an alternative. In this study, we show some unique features of quad...
The effects of off-resonance irradiation in nutation NQR experiments are demonstrated both experimentally and theoretically. The theoretical description of the off-resonance effects in 2D nutation NQR spectroscopy is given, and general exact formulas for the asymmetry parameter are obtained. It is shown that the outcome of the off-resonance nutation experiments depends on the data acquisition p...
Efficient Amplitude-Modulated Pulses for Triple- to Single-Quantum Coherence Conversion in MQMAS NMR
The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experime...
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