RELAXATION IN RUBY

1960 ◽  
Vol 38 (10) ◽  
pp. 1304-1317 ◽  
Author(s):  
R. A. Armstrong ◽  
A. Szabo
Keyword(s):  
Relaxation Time ◽  
Crystal Orientation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Cross Relaxation ◽  
Spin Lattice Relaxation ◽  
Signal Frequency ◽  
Spin Lattice ◽  
A Value ◽  
Frequency Ratios

The relaxation of the (1↔2) and (2↔3) transitions in chrome-doped Al2O3 (0.015%) has been studied at S-band, using a pulsed microwave method, over a range of crystal orientations in the magnetic field at temperatures of 77 deg;K to 50 deg;K, and at 4.2 deg;K and 1.6 deg;K. A T−7 variation of the relaxation time with temperature was found in the liquid nitrogen range. The relaxation time in this temperature range was found to be independent of crystal orientation, and for the (1↔2) transition was 50 microseconds at 77 deg;K. At liquid helium temperatures, harmonic cross relaxation was present over most of the range of the crystal orientation studied and was observed at harmonic-to-signal frequency ratios of 2:1, 3:2, and 1:2. The harmonic cross relaxation times were typically 10 to 100 times shorter than the lattice relaxation times, and were independent of temperature. At non-harmonic points at 4.2 deg;K, the spin–lattice relaxation could be described by one time constant, a value of 300 milliseconds being typical. At harmonic points anomalously long relaxation times as high as 12 seconds were observed.

A nuclear magnetic resonance investigation of three solid benzenes

1953 ◽  
Vol 218 (1135) ◽  
pp. 537-552 ◽  
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Second Moment ◽  
Spin Lattice ◽  
Second Moments ◽  
A Value

The nuclear magnetic resonance absorption spectrum and the spin-lattice relaxation time have been measured for the protons in three isotopic species of benzene in polycrystalline form between 75 and 278° K. The three species were C 6 H 6 , C 6 H 5 D and 1. 3. 5 - C 6 H 3 D 3 . For all three species the measured spectrum has its full rigid lattice width below 90° K. A method of analysis is developed which makes it possible to derive separately the intramolecular and the intermolecular contributions to the second moment (mean square width) of the spectrum from the measured second moments, without the necessity of knowing the crystal structure. From the intramolecular contribution it is found that the separation of neighbouring protons in the C 6 H 6 molecule is 2.495 ± 0.018 Å. The intermolecular contribution is in agreement with a value calculated from a knowledge of the crystal structure. On warming from 90 to 120°K the spectrum for all three species narrows considerably. From 120°K to the melting-point (278.7° K) the second moments remain almost constant. The second moment separation procedure is also applied in this range and leads to the conclusion that the narrowing is caused by reorientation of the molecules about their hexad axes in the crystal lattice. Analysis of the measurements of the spin-lattice relaxation time shows that for all three species the reorientation process is governed by an activation energy of 3.7 ± 0.2 kcal/mole. The reorientation frequency is of the order of 10 4 c/s at 85° K and rises to a value of the order of 10 11 c/s just below the melting-point. The relationship between the present experimental results and recent measurements of the Raman spectrum of solid benzene is discussed. Finally, consideration is given to the application to other materials of methods of separating the intra- and intermolecular contributions to the second moment.

SPIN LATTICE RELAXATION IN NEODYMIUM ETHYLSULPHATE AT LIQUID HELIUM TEMPERATURES

1960 ◽  
Vol 38 (5) ◽  
pp. 604-615 ◽  
Author(s):  
J. M. Daniels ◽  
K. E. Rieckhoff
Keyword(s):  
Relaxation Time ◽  
Faraday Effect ◽  
Pulse Length ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Approach To Equilibrium ◽  
Spin Lattice ◽  
Spin Populations ◽  
Adiabatic Magnetization

The optical Faraday effect was used to measure instantaneous magnetization in neodymium ethylsulphate. The spin populations were disturbed by pulses of microwave power, and by adiabatic magnetization and demagnetization, and the approach to equilibrium was studied. The relaxation was found to be exponential and spin lattice relaxation times were measured, for temperatures between 1.3° K and 4.2° K, and for magnetic fields between 80 and 6000 oersted. The relaxation time was found to decrease with increasing magnetic field, and to vary with temperature approximately as 1/T3. No dependence of relaxation time on pulse length was found.

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.

scholarly journals Reorientation of thiophene molecules in a benzene lattice

1978 ◽  
Vol 56 (5) ◽  
pp. 714-716 ◽  
Author(s):  
William E. Sanford ◽  
Robert K. Boyd ◽  
John A. Ripmeester
Keyword(s):  
Composition Range ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Intermolecular Forces ◽  
Spin Lattice Relaxation ◽  
Plane Rotation ◽  
Spin Lattice ◽  
A Value ◽  
Experimental Activation Energy ◽  
Thiophene Molecule

Benzene and thiophene are known to form solid solutions over the entire composition range; the present work demonstrates the orientational freedom of thiophene molecules in solid solution with excess perdeuterobenzene, through measurements of spin–lattice relaxation times. In addition, the atom–atom approximation to intermolecular forces yielded a potential energy profile for in-plane rotation of a thiophene molecule, embedded in a benzene lattice, which is consistent with the experimental activation energy for the relaxation. The second moment of the absorption signal for thiophene in perdeuterobenzene at 80 K was determined to be 0.66 G2, compared with a value of 0.42 G2 computed as the intramolecular contribution only for in-plane rotation

Nitrogen-14 quadrupole cross-relaxation spectroscopy

1988 ◽  
Vol 416 (1850) ◽  
pp. 149-178 ◽  
Keyword(s):  
Magnetic Field ◽  
Double Resonance ◽  
Relaxation Times ◽  
High Sensitivity ◽  
Lattice Relaxation ◽  
Cross Relaxation ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Spin Lattice ◽  
Quadrupole Resonance

Cross-relaxation spectroscopy can be used as a sensitive method of detecting 14 N quadrupole-resonance signals in hydrogen-containing solids. The 1 H spin system is polarized in a high magnetic field that is then reduced adiabatically to a much lower value satisfying the level­-crossing condition, when the 1 H Zeeman splitting matches one of the 14 N quadrupole splittings. If the 14 N spin–lattice relaxation time is much shorter than that of the 1 H nuclei, a drastic loss of 1 H polarization occurs that is measured by recording the residual 1 H magnetic resonance signal after the sample has been returned to the higher field. The experimental cycle can be run in several different ways according to the relative values of the 1 H spin–lattice relaxation times ( T 1 ) in high and low field, the 14 N spin–lattice relaxation ( T 1Q ) and cross-polarization times ( T CP ), all of which can markedly influence the spectra. The line shapes are broadened by the presence of the magnetic field and Zeeman shifts of the peak frequencies also occur, for which simple corrections may be derived. The methods used have high sensitivity, particularly if the ratio T 1 / T 1Q is large. They have the advantage over other double-resonance techniques in that long proton T 1 values are not necessary for the success of an experiment; it is also possible to select conditions in which the recovered 1 H signal is directly proportional to the relative numbers of 14 N nuclei present and the magnitude of the cross-relaxation field. Multi-proton relaxation jumps also give rise to signals at subharmonics of the fundamental, whose relative intensities reflect the extent to which the 14 N and 1 H relaxation is coupled via their dipole–dipole interactions, which are not completely quenched in the finite magnetic fields necessary in cross-relaxation spectroscopy. These conclusions are illustrated in a number of 14 N spectra of compounds in which quadrupole-resonance signals have not previously been recorded.

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.

MEASUREMENT OF SPIN-LATTICE RELAXATION AT 890 Mc/s BY A RESONANCE-DISPERSION TECHNIQUE

1965 ◽  
Vol 43 (4) ◽  
pp. 576-593 ◽  
Author(s):  
J. A. Carruthers ◽  
N. C. Rumin
Keyword(s):  
Relaxation Time ◽  
Modulation Frequency ◽  
Power Level ◽  
Relaxation Times ◽  
Audio Signal ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Degree Of Saturation ◽  
Multiple Time ◽  
Spin Lattice

A new technique has been used to measure the spin-lattice relaxation time of Cr+++ in K3Co(CN)6 at 890 Mc/s. The method depends on observing both the amplitude and phase of the audio signal developed at the modulation frequency in a bridge-type microwave resonance spectrometer. One or more modulation frequencies are used, depending on the value of the relaxation time and the degree of saturation employed. Although similar to the saturation technique, this method does not require knowledge of the power level or the linewidth, and is suited to measurements on weak lines. Results have been obtained for lines at 100, 300, 1 400, and 2 100 oersteds, using crystals containing 0.06% and 0.4% chromium. The values of T1 for the lower concentration are in the 20–30-millisecond range, but relaxation appears to be not equivalent to a single time-constant. For the higher concentration the relaxation times are shorter and there is a marked evidence of multiple time-constants.

13C NMR Investigations on the Stacking of 5′ -AMP with Tryptamine

1977 ◽  
Vol 32 (5-6) ◽  
pp. 315-320 ◽  
Author(s):  
V. Wray ◽  
K. G. Wagner
Keyword(s):  
Particle Size ◽  
Relaxation Time ◽  
Complex Formation ◽  
Ring Current ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Adenosine Monophosphate ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Abstract Stacking, Relaxation Time, Tryptamine, 5′-Adenosine Monophosphate Complex formation between 5′-adenosine monophosphate (5′-AMP) and tryptamine was in­ vestigated by measuring 13C chemical shifts and spin-lattice relaxation times. The chemical shift changes observed were attributed to ring current effects originating in the stacking of the two respective aromatic moieties and to puckering changes of the AMP ribose. Differences in the magnitude of the shifts of the aromatic carbons were related to the geometry of the complex and compared with those found for AMP selfassociation. Upon complex formation the relaxation times of especially the tryptamine indole carbons were greatly reduced, this was explained by an in­ crease in the particle size. Small changes found for the AMP carbons in solutions without tryptamine result from AMP selfassociation. Deviations from isotropic motion observed for the non-aromatic moieties are discussed.

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