INTENSITY OF NMR SIGNAL IN La1.90Sr0.10CuO4: CHARGE vs. SPIN FREEZING

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2791-2796
Author(s):  
M.-H. JULIEN ◽  
A. CAMPANA
Keyword(s):  
Spin Fluctuation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Simple Calculation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Superconducting Transition ◽  
Magnetic Fluctuations ◽  
Spin Lattice ◽  
Spin Freezing

We report on 139 La NMR and 63 Cu NQR measurements in La 1.90 Sr 0.10 CuO 4 above its superconducting transition temperature. We find that the intensity of the signal integrated on frequencies decreases significantly on cooling from 60 K to 28 K for 63 Cu nuclei (wipeout effect), while it remains constant for 139 La nuclei in this T-range. The distribution of 139 La spin-lattice relaxation time (T1) values in the "wipeout regime" reveals a spread of electronic fluctuation frequencies in CuO 2 planes. A simple calculation, for spin fluctuation induced relaxation, shows that 63 Cu nuclei at sites where electronic fluctuations are slowest should not be observable because of too short relaxation times. This means that the 63 Cu NQR wipeout effect may be explained primarily by slow magnetic fluctuations.

scholarly journals Possibilities of proton magnetic resonance in determination the cellulose crystallinity

2019 ◽  
Vol 59 (8) ◽  
pp. 116-123
Author(s):  
Yury B. Grunin ◽  
◽  
Maria S. Ivanova ◽  
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Active Surface ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Cellulose Crystallinity ◽  
Spin Lattice ◽  
Free Induction

A layered model of the structural organization of macrofibrils of native cellulose, consisting of microfibrils, which include elementary fibrils, has been developed. A feature of the proposed model is the presence of slit-like pores between the crystalline elements of cellulose. It was found that, on average, each water molecule interacts with one glucose residue of the surface chains of cellulose with the formation of hydrogen bonds in the framework of monolayer adsorption. This allows to establish a correlation between the cellulose crystallinity and the capacity of the adsorption water monolayer on its active surface. Based on the condition of rapid molecular exchange between the adsorption water layers in the framework of the Bloembergen-Purcell-Pound theory, an approach is proposed for determination the capacity of water monolayer. The obtained values are consistent with the results of solving the Brunauer-Emmett-Teller equation for the adsorption isotherm of water on the active surface of cellulose. The Fourier transform of the free induction decay signal of cellulose allows to estimate its crystallinity at various moisture contents. Methods have been developed for assessing the crystallinity of different types of dry cellulose based on NMR relaxation parameters — spin-lattice relaxation time and spin-spin relaxation time. Using the method of deuteration of cellulose, the relaxation times of its crystalline regions were determined. The results of preliminary studies showed that the crystallinity of cotton cellulose is higher in comparison with the same parameter of woody types of cellulose. A comparison of the literature and the data we obtained using 1H-NMR relaxation confirmed the possibility of utilizing the developed methods to solve the tasks of scientific research and conducting quality control of cellulosic materials at specialized enterprises.

Carbon-13 Spin–Lattice Relaxation Times for Selected Steroids

1975 ◽  
Vol 53 (3) ◽  
pp. 338-342 ◽  
Author(s):  
John W. ApSimon ◽  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Conformational Changes ◽  
Correlation Time ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
Molecular Correlation ◽  
Anisotropic Motion

The spin–lattice relaxation time (T1) data for a number of androstane and cholestane derivatives is presented. The NT1 value of carbon-3 in several of the compounds is found to be shorter than the average NT1 value for the other ring carbons which is interpreted in terms of anisotropic motion with the long steroid axis being the preferred axis of rotation. As this effect is only observed for carbon-3, an effective molecular correlation time can be calculated from the average NT1 value for all other CH and CH2 carbons. The correlation time (τi) for internal rotation of a methyl group is shown to depend on the number of 1,3 diaxial methyl group – hydrogen interactions. Thus τi(C-19) is shorter than τi(C-18) for androstane, τi(C-19) is shorter for trans-cholestanol than for either cis-cholestanol or cholesterol. The effects of substituents and conformational changes on τi as well as the effect of solvent on T1 are discussed.

Ionic Dynamics in Plastic Crystal KNO2 Studied by 39K and 15N NMR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
Motoko Kenmotsu ◽  
Hisashi Honda ◽  
Hiroshi Ohki ◽  
Ryuichi Ikeda ◽  
Tomoki Erata ◽  
...  
Keyword(s):  
Intermediate Phase ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
15N Nmr ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice

AbstractThe spin-lattice relaxation time of 39K NMR observed in the low-temperature phase (T<264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2- motion. The in-plane C3 reorientation and the overvall NO2 rotation as well as the self-diffusion were shown in the intermediate phase (T ≤ 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing 39K and 15N NMR relaxation times and 15N lineshapes.

Quadrupolar Relaxation of X Type Nuclei in R2MX6 and RMX3 Compounds

1975 ◽  
Vol 53 (12) ◽  
pp. 1141-1147 ◽  
Author(s):  
Henry M. van Driel ◽  
Robin L. Armstrong
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Mode Spectrum ◽  
Spin Lattice ◽  
Raman Process ◽  
Quadrupole Resonance ◽  
Quadrupolar Relaxation

Calculations of nuclear quadrupolar spin–lattice relaxation times are presented. The expressions obtained for the first order Raman and anharmonic Raman processes are applicable to a pure nuclear quadrupole resonance investigation of the X nuclei in R2MX6 and RMX3 solids. On the basis of realistic assumptions it is shown that the anharmonic Raman process will provide the dominant relaxation mechanism for these nuclei in these compounds. The relation between the spin–lattice relaxation time and the lattice dynamics is obtained explicitly without recourse to an assumed form of lattice vibrational normal mode spectrum. In favorable cases it is shown that the spin–lattice relaxation times can be related to Brillouin zone averaged rotary mode frequencies which are useful for the analysis of experimental data.

Investigation of the 1H Spin-Lattice Relaxation in Polycrystalline NH4ReO4 Induced by Mechanical Sample Rotation

1976 ◽  
Vol 31 (12) ◽  
pp. 1707-1710 ◽  
Author(s):  
H. Rager
Keyword(s):  
Relaxation Times ◽  
Larmor Frequency ◽  
Rotation Frequency ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Sample Rotation ◽  
Resonance Frequencies

Abstract Measurements of the proton spin-lattice relaxation time, T1 , in polycrystalline NH4ReO4 have shown that mechanical sample rotation in the static magnetic field reduces T1 for proton magnetic resonance frequencies within the range 30 - 42 MHz. The rotation induced proton spin-lattice relaxation times, T1′, were measured at different Larmor frequencies, sample rotation frequencies, and temperatures. At room temperature T1′ increases with increasing proton Larmor frequency. The dependence of T1′ on sample rotation frequency and temperature is small. The "normal" proton T1 times were determined as a function of temperature at 30 and 42 MHz. From these measurements an average activation energy of 2.4 kcal/mole was obtained for the NH4+ reorientation. The "normal" spin-lattice relaxation behavior was observed to be non-exponential at 30 MHz above 200 K and at 42 MHz above 260 K and is nearly independent on temperature above 300 K.

Activation Energies for Fluxional Behavior in Aryl(pentachlorocyclopentadienyl)mercurials, η1 -C5Cl5 HgR, from 35Cl NQR Relaxation Times

1990 ◽  
Vol 45 (3-4) ◽  
pp. 503-510 ◽  
Author(s):  
Norbert Weiden ◽  
Alarich Weiss ◽  
Gary Wulfsberg ◽  
William Ilsley ◽  
William Ilsley ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Activation Energies ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
35Cl Nqr ◽  
C Nmr ◽  
Phenyl Mercury

Abstract Solid-state activation energies for fluxional behavior in three aryl-subsituted (pentachlorocyclo-pentadienyl)phenylmercury compounds RHgC5 Cl5 : (pentachlorocyclopentadienyl)(pentamethyl-phenyl)mercury (I, R = C6 (CH3)5 , Eact = 19.3 kJ mol-1); (pentachlorocyclopentadienyl)(2,4,6-tris-(terf-butyl)phenyl)mercury (II, R = 2,4,6-C 6 H 2 (C(CH3)3)3 , Eact = 59.5 kJ mol-1); and (pentachloro-cyclopentadienyl)(phenyl)mercury (III, R = C6H5 , E act = 62.8 kJ mol-1) have beeb obtained from 35Cl NQR spin-lattice relaxation-time measurements. II has also been shown to be fluxional in solution by 13C NMR spectra. II was prepared by an exchange reaction between Hg(C5Cl5)2 and Hg(2,4,6-C6H2(C(CH3)3)3)2 , which reacted readily despite the great steric hindrance present in the latter reagent.

Proton NMR Spin-Lattice Relaxation Time Characterization of a-Si(H) Structure

1980 ◽  
Vol 3 ◽  
Author(s):  
M. E. Lowry ◽  
R. G. Barnes ◽  
D. R. Torgeson ◽  
F. R. Jeffrey
Keyword(s):  
Relaxation Time ◽  
Room Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Mixed Phase ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nmr Data

ABSTRACTNMR data are presented for reactively sputtered amorphous silicon-hydrogen alloys (a-Si(H)). Measured differences in two of the samples are attributed to two distinct morphologies: a mixed phase (monohydride and dihydride) and a purely monohydride composition. Features of the mixed phase morphology have been modeled. Room temperature, 35 MHz spin-lattice relaxation times are presented for a series of monohydride samples prepared with systematically varied sputtering parameters. A correlation of proton T1 with the density of ESR states tentatively is suggested.

Carbon-13 NMR and Raman Scattering Studies of Potassium Propoxybenzoate and Potassium Butoxybenzoate. Conformational Change Due to Micellization

1981 ◽  
Vol 36 (12) ◽  
pp. 1352-1356
Author(s):  
Hirofumi Okabayashi ◽  
Tadayoshi Yoshida ◽  
Yukimasa Terada ◽  
Teruki Ikeda ◽  
Kazuhiro Matsushita
Keyword(s):  
Conformational Change ◽  
Chemical Shifts ◽  
Deuterium Oxide ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Alkoxy Group ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Methylene Groups

Abstract Carbon-13 NMR chemical shifts and carbon-13 spin-lattice relaxation times of potassium propoxybenzoate and potassium butoxybenzoate in deuterium oxide solution were measured at various concentrations. For the alkoxy group, the earbon-13 resonance peak of the O-CH2 segment is shifted rapidly up-field upon micellization, while the resonance peaks of other methylene groups are shifted downfield. This observation is ascribed to the conformational change of the alkoxy group on micellization. In the monomolecular solution of potassium butoxybenzoate, the restricted state of the O-CH2 bond was estimated by carbon-13 spin-lattice relaxation time measurement. It was also found that micellization brings about a further restricted internal rotation about the O-CH2 bond.

Role of Paramagnetic Ions and Water Proton Spin-Lattice Relaxation Time in Biological Systems

1993 ◽  
Vol 32 (01) ◽  
pp. 52-56 ◽  
Author(s):  
S. F. Akber
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Manganese Concentration ◽  
Water Proton ◽  
Manganese Ion ◽  
Spin Lattice ◽  
Paramagnetic Ions

SummaryThis paper summarizes the observations of different studies concerning the influence of paramagnetic ions on spin-lattice relaxation times in magnetic resonance imaging. Based on findings that manganese ion content in cancer tissues is decreased in comparison to normal tissues, the results of different papers analysing the influence of tissue manganese concentration on spin- lattice relaxation times are collected and compared. Neither the comparison between different organs, different animals nor the comparison between different tissues (normal and malignant) showed correlations of practical consequences between manganese concentrations and spin-lattice relaxation times. These results are consistent with those from studies with copper and iron ions in living systems.

Chlorine Nuclear Quadrupole Relaxation and Cationic Motion in Trimethylsulfonium Hexachloroselenate(IV): [(CH3)3S]2SeCl6

1992 ◽  
Vol 47 (1-2) ◽  
pp. 274-276
Author(s):  
Makoto Kaga ◽  
Tetsuo Asaji ◽  
Ryuichi Ikeda ◽  
Daiyu Nakamurab
Keyword(s):  
Complex Anion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Quadrupole Relaxation ◽  
Spin Lattice ◽  
Nuclear Quadrupole ◽  
Increasing Temperature ◽  
Nuclear Quadrupole Relaxation

AbstractThe 35Cl NQR spin-lattice and spin-spin relaxation times, T1Q and T2Q, respectively, and the 1HNMR spin-lattice relaxation time T1H at 32 and 60 MHz were determined for [(CH3)3S]2SeCl6 as functions of temperature. The rapid decrease of observed above ca. 250 K with increasing temperature was attributed to the onset of reorientation of the [SeCl6 ]2- complex anion with the activation energy Ea = 42 + 5 kJ mol -1 . When cooled from ca. 250 K, T1Q showed an anomalous decrease. This T1Q decrease was explained by electric field gradient modulation related to some cationic motion. Possible origins of the cationic motion are discussed

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