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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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Journal ArticleDOI
TL;DR: In this paper, the spin structure of Cu at low temperatures is suggested to be a simple antiferromagnet with sublattice moments parallel to the a-axis.
Abstract: Rather complex Nuclear Quadrupole Resonance (NQR) spectrum of 139 La in La 2 CuO 4-δ , observed at low temperatures is successfully interpreted as a signal from a single La site which suffers a combined effect of a quadrupole coupling (coupling constant ν Q =6.38±0.02 MHz with asymmetry parameter η=0.01±0.01) and a small Zeeman term where the internal field ( H N =0.997±0.010 kOe) is nearly perpendicular to the direction of the maximum field gradient. The spin structure of Cu at low temperatures is suggested to be a simple antiferromagnet with sublattice moments parallel to the a -axis. The temperature dependences of ν Q and H N have been measured in detail. The fractional decrease of H N which is proportional to the Cu sublattice moments is found to be in general accord with the prediction of spin fluctuations theory for weak itinerant antiferromagnets.

45 citations

Proceedings ArticleDOI
28 Mar 1994
TL;DR: In this paper, a proof-of-concept pure nuclear quadrupole resonance (NQR) detector for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin is presented.
Abstract: Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a proof-of-concept NQR explosives detector which interrogates a volume of 300 liters (10 ft3). With minimal modification to the existing explosives detector, we can detect operationally relevant quantities of (free base) cocaine within the 300-liter inspection volume in 6 seconds. We are presently extending this approach to the detection of heroin base and also examining 14N and 35,37Cl pure NQR for detection of the hydrochloride forms of both materials. An adaptation of this NQR approach may be suitable for scanning personnel for externally carried contraband and explosives. We first outline the basics of the NQR approach, highlighting strengths and weaknesses, and then present representative results for RDX and cocaine detection. We also present a partial compendium of relevant NQR parameters measured for some materials of interest.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

45 citations

Journal ArticleDOI
TL;DR: The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements, and its vibrational properties studied with Raman spectroscopy.
Abstract: SrCu2(PO4)2 was prepared by the solid-state method at 1153 K. Its structure was solved by direct methods in the space group Pccn (No. 56) with Z = 8 from synchrotron X-ray powder diffraction data measured at room temperature. Structure parameters were then refined by the Rietveld method to obtain the lattice parameters, a = 7.94217(8) A, b = 15.36918(14) A, and c = 10.37036(10) A. SrCu2(PO4)2 presents a new structure type and is built up from Sr2O16 and Cu1Cu2O8 units with Cu1...Cu2 = 3.256 A. The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements. With spin-dimer analysis, it was shown that the two strongest spin-exchange interactions between Cu sites result from the Cu1-O...O-Cu2 and Cu2-O...O-Cu2 super-superexchange paths with Cu1...Cu2 = 5.861 A and Cu2...Cu2 = 5.251 A, and the superexchange associated with the structural dimer Cu1Cu2O8 is negligible. The magnetic susceptibility data were analyzed in terms of a linear four-spin cluster model, Cu1-Cu2-Cu2-Cu1 with -2J(1)/kB = 82.4 K for Cu1-Cu2 and -2J(2)/k(B) = 59 K for Cu2-Cu2. A spin gap deduced from this model (Delta/kB = 63 K) is in agreement with that obtained from the Cu NQR data (Delta/kB = 65 K). A one-half magnetization plateau was observed between approximately 50 and 63 T at 1.3 K. Specific heat data show that SrCu2(PO4)2 does not undergo a long-range magnetic ordering down to 0.45 K. SrCu2(PO4)2 melts incongruently at 1189 K. We also report its vibrational properties studied with Raman spectroscopy.

45 citations

Journal ArticleDOI
TL;DR: The theory of pure spin-1 nuclear quadrupole resonance (NQR) excitation and detection is presented with comparisons to nuclear magnetic resonance as mentioned in this paper, where the spin dynamics are isolated to two resonant energy levels, leading to close parallels in the calculations of their respective signals.
Abstract: The theory of pure spin-1 nuclear quadrupole resonance (NQR) excitation and detection is presented with comparisons to nuclear magnetic resonance (NMR). Even though the dominating Hamiltonians in pure NQR and NMR have different symmetry properties, in both single resonant frequency spin-1 NQR and spin-½ NMR the spin dynamics are isolated to two resonant energy levels, leading to close parallels in the calculations of their respective signals. The theory of spin-1 NQR is presented in terms of matrix calculations and fictitious spin-½ operators, and the analysis focuses on the similarities and differences of the spin-1 NQR and spin-½ NMR physical interpretations and rotational symmetry properties. © 2002 Wiley Periodicals, Inc. Concepts in Magn Reson 14, 155–171, 2002.

44 citations


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