Investigation of the central line of 93Nb by a two-dimensional NMR method (original) (raw)
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Spectroscopy ofNb90at high spin
Physical Review C, 2005
Excited states of 90 Nb were investigated via prompt and delayed γ decays and the recoil-isomer tagging technique. The level scheme of 90 Nb has been extended up to J = 19h and E x = 8.4 MeV. Half-lives of the 11 − and 17/2 − isomeric levels in 90,91 Nb were measured to be 0.47 ± 0.01 and 3.3 ± 0.4 µs, respectively. The results are compared with the predictions of large-basis shell model calculations. The effects of truncation of the valence model space on the calculated results are discussed.
NMR line shapes from AB spin systems in solids — The role of antisymmetric spin–spin coupling
Canadian Journal of Chemistry, 2009
NMR parameters such as indirect nuclear spin–spin coupling (J), nuclear magnetic shielding (σ), direct dipolar coupling (D), and electric field gradient (V) are properly described by second-rank tensors. Each may be decomposed into isotropic, symmetric, and antisymmetric components; the number of these three components which may be nonzero is a distinguishing attribute of each interaction tensor. The rank-1 antisymmetric portion of J (Janti) holds the distinction of remaining the only nonzero part of these fundamental NMR interaction tensors which has never been observed experimentally. Accordingly, effects from Janti are usually ignored, but it is important to consider when this is valid. An experimental strategy for observing Janti in powdered samples of tightly coupled homonuclear spin pairs, based on ideas originally presented by Andrew and Farnell ( Mol. Phys. 1968, 15, 157 ), is described. The theory of Andrew and Farnell is extended to powder samples, and methods for analyzin...
b-detected NMR of 8 Li in the normal state of 2H-NbSe 2
b-NMR of isolated 8 Li has been investigated in the normal state of 2H-NbSe 2. In a high magnetic field of 3 T a single resonance is observed with a Gaussian line width of 3.5 kHz. The line shape varies weakly as function of magnetic field and temperature but has a strong orientation dependence. The nuclear electric quadrupole splitting is unresolved implying that the electric field gradients are 10–100 times smaller than in other non-cubic crystals. The nuclear spin relaxation rate is also anomalously small but varies linearly with temperature as expected for Korringa relaxation in a metal. These results suggest that Li adopts an interstitial position between the weakly coupled NbSe 2 layers and away from the conduction band.
Nuclear resonance studies of 95 Nb Fe
Hyperfine Interactions, 1977
Dilute alloys of 35-day95Nb in polycrystalline iron have been studied by nuclear magnetic resonance on oriented nuclei (NMR/ON) using frequency modulation and fast passage techniques. Comparison of resonance frequencies with nuclear orientation results confirms the spin 9/2 for the95Nb ground state. The zero-field resonance frequency is 275.29(9) MHz, leading to ag-factor of 1.3653(25) if the hyperfine field from spin-echo measurements on93NbFe is used. Relaxation times, line shapes, and the frequencyversus field behavior are discussed. A summary of data for CoFe alloys, used here for calibration purposes, is also given.
High-spin states in the 94Nb nucleus
Physical Review C, 2000
High-spin states have been studied for the first time in the 94 Nb nucleus with the reaction 82 Se( 19 F,␣3n␥) at 68 MeV. A cascade of transitions has been observed, based on the (6) ϩ ground state and extending up to 6.5 MeV excitation and spin of about 19.
The Journal of Physical Chemistry, 1990
The spin lattice relaxation time, T , , quadrupolar coupling constant, and chemical shielding tensor elements of several for IH's. Typical relaxation times for 87Rb are in the range of 100-300 ms and 50-300 ms for 85Rb. The Q , values are in the range of 7-14 MHz for 85Rb and 3-1 1 MHz for 87Rb. A program was created to numerically simulate and fit experimental powder patterns for the &/2 central transition, where the principal axis systems (PAS) of the shielding and quadrupole tensors are not coincident. The analysis shows that having both nuclides available with significantly different quadrupole coupling constants makes the general line-shape problem more tractable. That is, the 85Rb data provides an excellent visualization of chemically different rubidium atoms when there are significant differences in the value of Q , . Such data would be difficult to extract from the corresponding 87Rb line shapes due to the smaller value of Q , . The 87Rb nuclide, however, because of its smaller value of Qa, provides an excellent opportunity to observe the consequences of the noncoincident PAS frames between the shielding and quadrupole tensors. rubidium salts have been surveyed at the frequency 130.88 MHz for 9, ' 7Rb and 38.64 MHz for 85Rb, i.e. 9.4T, or 400 MHz ( 5 ) Baugher, J. F.; Taylor, P. C.; Oja, T.; Bray, P. J. J. Chem. Phys. 1969, 11. 4914. 0022-3654/90/2094-0553$02.50/0 -0 1990 American Chemical Societv ( 6 ) Mehring, M. The Principles of High Resolution N M R in Solids, 2nd ed.: New York Press: 1976.
Narrowband Excitation of 2H Powder Pattern and Its Application to 2H 1D Exchange Sample-Turning NMR
Journal of Magnetic Resonance, 1999
Frequency-selective narrowband excitation of the 2 H powder pattern was examined. Selection of a single spectral band with a linewidth of ca. 15 kHz was achieved by a narrowband 1 H 3 2 H cross polarization by using the time-averaged precession frequency method. Further narrowing with a ca. 5 kHz linewidth is achieved by DANTE irradiation. The narrowband excitation was applied to transform a recently developed 2D spin-exchange method for obtaining structural information (Chem. Phys. Lett. 260, 159, (1996)) into its 1D analogue. The determination of the D-C-D bond angle was demonstrated for ␣-glycine-[2,2-d 2 ]. Further, the intermolecular polarization transfer between two deuterons separated by 0.299 nm was detected with the mixing time of 500 ms.
Exact expression for the spin 7/2 line intensities: Application to solid state 59 Co(III) NMR
Molecular Physics, 1994
The density matrix of a spin I = 7/2, excited by a radiofrequency pulse, is calculated in taking into account the first order quadrupolar interaction during the excitation. Therefore, the results are valid for any ratio of the quadrupolar coupling ~% to the pulse amplitude ~ORF. The behaviour of the central line intensity versus the pulse length is discussed both in time and frequency domains. The quadrupolar coupling constant e2qQ/h = 8.24 MHz of the 59Co(III) nucleus in a polycrystalline sample of Na3[Co(NO2)6] is determined using this onedimensional nutation method, and the lineshape reveals mainly the presence of chemical shift anisotropy with axial symmetry.
detected NMR of 8Li in the normal state of 2H
Physica B: Condensed Matter, 2006
b-NMR of isolated 8 Li has been investigated in the normal state of 2H-NbSe 2 . In a high magnetic field of 3 T a single resonance is observed with a Gaussian line width of 3.5 kHz. The line shape varies weakly as function of magnetic field and temperature but has a strong orientation dependence. The nuclear electric quadrupole splitting is unresolved implying that the electric field gradients are 10-100 times smaller than in other non-cubic crystals. The nuclear spin relaxation rate is also anomalously small but varies linearly with temperature as expected for Korringa relaxation in a metal. These results suggest that Li adopts an interstitial position between the weakly coupled NbSe 2 layers and away from the conduction band. r