Bewegungen der CH3-Gruppen in Methyl-Naphthalin-Kristallen

1972 ◽  
Vol 27 (1) ◽  
pp. 42-50 ◽  
Author(s):  
J. U. Von Schütz ◽  
H. C. Wolf
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Activation Energies ◽  
Rotational Barrier ◽  
Proton Relaxation ◽  
Methyl Groups ◽  
Hindered Rotation ◽  
Proton Relaxation Time ◽  
Methyl Naphthalene ◽  
The Magnetic Field

Abstract The longitudinal proton relaxation time T1 in methyl naphthalene crystals, differing in the arrangement and number of the substituted CH3 groups, was measured as a function of the temperature above 77 °K and the magnetic field between 0.9 and 20 kOe. The results can be described by hindered rotation of the methyl groups with the jumping times and activation energies strongly dependent on the group arrangement. In the β-position the rotational barrier of 0.8 kcal/mol is predominantly determined by the infermolecular interaction, whereas in the case of the a-position and for adjacent CH3’s the hindering potential of 2.4 kcal/mol arises largely from the intramolecular term.

High magnetic field NMR investigation of the spin density wave phase of TMTSF2PF6

2002 ◽  
Vol 12 (9) ◽  
pp. 389-389
Author(s):  
W. G. Clark ◽  
F. Zamborsky ◽  
B. Alavi ◽  
P. Vonlanthen ◽  
W. Moulton ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Proton Relaxation ◽  
High Magnetic Fields ◽  
Organic Conductor ◽  
First Order ◽  
The Magnetic Field ◽  
Very High

We report proton NMR measurements of the effect of very high magnetic fields up to 44.7 T (1.9 GHz) on the spin density wave (SDW) transition of the organic conductor TMTSF2PF6. Up to 1.8 GHz, no effect of critical slowing close to the transition is seen on the proton relaxation rate (1/T1), which is determined by the SDW fluctuations associated with the phase transition at the NMR frequency. Thus, the correlation time for such fluctuations is less than $1O^{-10}$s. A possible explanation for the absence of longer correlation times is that the transition is weakly first order, so that the full critical divergence is never achieved. The measurements also show a dependence of the transition temperature on the orientation of the magnetic field and a quadratic dependence on its magnitude that agrees with earlier transport measurements at lower fields. The UCLA part of this work was supported by NSF Grant DMR-0072524.

The Effects of the Method of Death and Lapsed Time on Proton Relaxation Time T1 in Autopsied Muscle Samples

1993 ◽  
Vol 28 (6) ◽  
pp. 529-532 ◽  
Author(s):  
ANU M. ALANEN ◽  
RIITA K. PARKKOLA ◽  
IRIS G.V. LILLSUNDE ◽  
KIMMO O.J. VIRTANEN ◽  
HANNU O. KALIMO ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Proton Relaxation ◽  
Proton Relaxation Time

Anisotropy of the proton relaxation time T in TMMC

1974 ◽  
Vol 48 (4) ◽  
pp. 295-297 ◽  
Author(s):  
Y.H. Tchao ◽  
S. Clement
Keyword(s):  
Relaxation Time ◽  
Proton Relaxation ◽  
Proton Relaxation Time

Effects of cytoskeletal inhibitors on water proton relaxation time changes in unfertilized and fertilized sea urchin eggs

1987 ◽  
Vol 11 (8) ◽  
pp. 605-614 ◽  
Author(s):  
S ZIMMERMAN ◽  
A ZIMMERMAN ◽  
I CAMERON ◽  
G FULLERTON ◽  
H SCHATTEN ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Sea Urchin ◽  
Water Proton ◽  
Proton Relaxation ◽  
Proton Relaxation Time ◽  
Sea Urchin Eggs ◽  
Time Changes

emperature Dependence of the Magnetoresistance Effect in Metals

2012 ◽  
Vol 67 (8-9) ◽  
pp. 498-508
Author(s):  
Stanisław Olszewski
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Metal Temperature ◽  
Time Increase ◽  
Electric Conduction ◽  
Magnetoresistance Effect ◽  
Metal Sample ◽  
The Magnetic Field

The paper examines a well-known experimental property of increase of the magnetoresistance effect in a metal observed with a decrease of the metal temperature. This property is explained by the fact that magnetoresistance is a quantity proportional to the relaxation time of the electric conduction of the metal sample which is a parameter observed in the absence of the magnetic field. Since the electric conduction, as well as the corresponding relaxation time, increase with the lowering of temperature, they provide us necessarily with an increase of magnetoresistance. The phenomenon is investigated quantitatively in this paper for numerous metal cases taken as examples.

Significance of proton relaxation time measurement in brain edema, cerebral infarction and brain tumors

1986 ◽  
Vol 4 (4) ◽  
pp. 293-304 ◽  
Author(s):  
Shoji Naruse ◽  
Yoshiharu Horikawa ◽  
Chuzo Tanaka ◽  
Kimiyoshi Hirakawa ◽  
Hiroyasu Nishikawa ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Brain Tumors ◽  
Cerebral Infarction ◽  
Brain Edema ◽  
Time Measurement ◽  
Proton Relaxation ◽  
Proton Relaxation Time ◽  
Relaxation Time Measurement

MAGNETORESISTANCE IN COPPER

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4434-4441
Author(s):  
SHIGEJI FUJITA ◽  
NEBI DEMEZ ◽  
JEONG-HYUK KIM ◽  
H. C. HO
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Kinetic Theory ◽  
Anisotropic Magnetoresistance ◽  
Magnetic Field Direction ◽  
Conduction Electrons ◽  
Fcc Lattice ◽  
A Charge ◽  
The Magnetic Field ◽  
Cyclotron Mass

The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e2ncτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, nc the density of the conduction electrons, and τ the relaxation time. The density nc depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

DEPHASING IN PRESENCE OF A MAGNETIC FIELD

2007 ◽  
Vol 06 (03n04) ◽  
pp. 261-264 ◽  
Author(s):  
A. V. GERMANENKO ◽  
V. A. LARIONOVA ◽  
I. V. GORNYI ◽  
G. M. MINKOV
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Relaxation Rate ◽  
Negative Magnetoresistance ◽  
Phase Relaxation ◽  
Quasi Momentum ◽  
Fitting Procedure ◽  
Electron Interference ◽  
Momentum Relaxation ◽  
The Magnetic Field

Effect of the magnetic field on the rate of phase breaking is studied. It is shown that the magnetic field resulting in the decrease of phase relaxation rate [Formula: see text] makes the negative magnetoresistance due to suppression of the electron interference to be smoother in shape and lower in magnitude than that found with constant [Formula: see text]-value. Nevertheless our analysis shows that experimental magnetoconductance curves can be well fitted by the Hikami–Larkin–Nagaoka expression.1 The fitting procedure gives the value of τ/τϕ, where τ is the quasi-momentum relaxation time, which is close to the value of τ/τϕ(B = 0) with an accuracy of 25% or better when the temperature varies within the range from 0.4 to 10 K. The value of the prefactor α found from this procedure lies within the interval 0.9–1.2.

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