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Nuclear quadrupole resonance

About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.


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TL;DR: In this paper, the effects of lithium doping on the spin dynamics in the paramagnetic and in the antiferromagnetic (AF) phase were investigated, and it was argued that Li enters in the CuO lattice up to a doping around 4%.
Abstract: [sup 63]Cu nuclear quadrupole resonance (NQR), nuclear antiferromagnetic resonance (AFNMR), and spin-lattice relaxation, as well as [sup 7]Li NMR and relaxation measurements in CuO and in Cu[sub 1[minus][ital x]]Li[sub [ital x]]O, are used to study the spin dynamics in the paramagnetic and in the antiferromagnetic (AF) phase, and in particular the effects induced by lithium doping. It is argued that Li enters in CuO lattice up to a doping [ital x] around 4%; from a comparison of the electric-field gradient (EFG) and of the dipolar field at the nucleus with theoretical estimates, it appears that Li[sup +] is slightly displaced from the Cu lattice site. From NQR, NMR, and AFNMR spectra, information on the Cu hyperfine interaction and the EFG are derived. The Neel temperature [ital T][sub [ital N]] is affected by Li doping to a moderate extent, decreasing from 226 K in CuO to [ital T][sub [ital N]]=183 K for [ital x]=3.7%. The relaxation rates, driven by the time-dependent part of the magnetic electron-nucleus Hamiltonians, indicate that the Cu[sup 2+] spin dynamics is almost unaffected by Li doping for [ital T][much gt][ital T][sub [ital N]] and possibly controlled by valence fluctuations. The Li doping modifies in a dramatic waymore » the spin fluctuations in the AF phase.« less

28 citations

Journal ArticleDOI
TL;DR: In this paper, three nuclear quadrupole resonance lines were observed in chloral hydrate at temperatures 20-300K, the frequencies being 38.2863±0.0004 MHz(ν1), 39.5415± 0.0002(ν2), and 39.6252± 0.0002(π).
Abstract: Three nuclear quadrupole resonance lines were observed in chloral hydrate at temperatures 20–300K, the frequencies being 38.2863±0.0004 MHz(ν1), 39.5415±0.0002(ν2), and 39.6252±0.0002(ν3) at 20.3K. Their temperature dependence was measured below 77K, showing monotonous decrease with increasing temperature. The difference in frequency between ν1 and ν2(or ν3) is probably due to a crystal field effect rather than OH···Cl hydrogen bonding as has been suggested. The spin-lattice relaxation time for all the lines, determined by pulse techniques, coincides with each other and tends to decrease rapidly above 250K. The decrease was interpreted as arising from hindered internal rotation of the CCl3 group with the activation energy of 8.8 kcal mol−1.

28 citations

Journal ArticleDOI
TL;DR: A set of robust algorithms, allowing for uncertainties in the assumed amplitudes of the NQR signal components are developed, showing that these offer a significant performance gain over the current state-of-the art techniques.
Abstract: Nuclear quadrupole resonance (NQR) is a solid-state radio frequency spectroscopic technique that can be used to detect compounds which contain quadrupolar nuclei, a requirement fulfilled by many high explosives and narcotics. Unfortunately, the low signal-to-noise ratio (SNR) of the observed signals currently inhibits the widespread use of the technique, thus highlighting the need for intelligent processing algorithms. In earlier work, we proposed a set of maximum likelihood-based algorithms enabling detection of even very weak NQR signals. These algorithms are based on derived realistic NQR data models, assuming that the (complex) amplitudes of the NQR signal components are known to within a multiplicative constant. However, these amplitudes, which are obtained from experimental measurements, are typically prone to some level of uncertainty. For such cases, these algorithms will experience a loss in performance. Herein, we develop a set of robust algorithms, allowing for uncertainties in the assumed amplitudes, showing that these offer a significant performance gain over the current state-of-the art techniques.

28 citations

Journal ArticleDOI
TL;DR: In this paper, a pressure dependence of the 63 Cu nuclear quadrupole resonance (NQR) frequency, ν Q, and T c have been measured for La 1.85 Sr 0.15 CuO 4 and YBa 2 Cu 4 O 8 under high pressure up to 1.3GPa.

27 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202237
202116
202036
201928
201829