Frequency dependence of the proton spin relaxation of the dipolar energy in a liquid crystal

1973 ◽  
Vol 59 (1) ◽  
pp. 460-462 ◽  
Author(s):  
A. R. Sharp ◽  
W. F. Forbes ◽  
M. M. Pintar
Keyword(s):  
Liquid Crystal ◽  
Frequency Dependence ◽  
Spin Relaxation ◽  
Proton Spin

Frequency Dependence of Proton Spin Relaxation in Liquid Crystalline PAA

1975 ◽  
Vol 30 (4) ◽  
pp. 437-441 ◽  
Author(s):  
W. Wölfel ◽  
F. Noack ◽  
M. Stohrer
Keyword(s):  
Relaxation Time ◽  
Transition Temperature ◽  
Frequency Dependence ◽  
Spin Relaxation ◽  
Correlation Time ◽  
Liquid Crystalline ◽  
Larmor Frequency ◽  
Proton Spin ◽  
Isotropic Phase ◽  
Frequency Range

Abstract We report on measurements of the Larmor frequency dependence of the proton spin relaxation time T1 in the nematic and isotropic phase of p-azoxyanisole (frequency range: 3.8 kHz ≦ ωL/2 π≦75 MHz) . In both cases our results clearly support the Pincus-Cahane mechanism of spin relaxation by order fluctuations ("ωL−½-law") and exclude the alternative translational dif­fusion model (“ωL+½-law”). For the isotropic phase it was possible to evaluate the correlation time τ of the liquid crystalline order fluctuations from the observed T1 dispersion. As a function of the deviation ⊿ν=ν-νc from the critical nematic-isotropic transition temperature, νc= (136± 0.5)°C, we found τ=2.71·10-7-⊿ν-0.25s .

Proton Spin Relaxation in the Liquid Crystal PAA

1971 ◽  
Vol 55 (1) ◽  
pp. 145-151 ◽  
Author(s):  
Ronald Y. Dong ◽  
W. F. Forbes ◽  
M. M. Pintar
Keyword(s):  
Liquid Crystal ◽  
Spin Relaxation ◽  
Proton Spin

Proton spin relaxation in a smectic liquid crystal

1974 ◽  
Vol 25 (2) ◽  
pp. 299-301 ◽  
Author(s):  
Ronald Y. Dong ◽  
M. Wiszniewska ◽  
E. Tomchuk ◽  
E. Bock
Keyword(s):  
Liquid Crystal ◽  
Spin Relaxation ◽  
Proton Spin ◽  
Smectic Liquid Crystal

Frequency dependence of nuclear spin relaxation in paramagnetic transition-metal complexes

1976 ◽  
Vol 29 (9) ◽  
pp. 1885 ◽  
Author(s):  
DT Pegg ◽  
DM Doddrell
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Frequency Dependence ◽  
Transition Metal Complexes ◽  
Spin Relaxation ◽  
Nuclear Spin ◽  
Relaxation Times ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Zero Field

Proton spin-lattice relaxation times have been determined as a function of magnetic field strength (H0) for a series of paramagnetic transition-metal complexes chosen so that, for some, the electron spin relaxation times (te) fall in the Redfield limit (te � tr) while for others te << tr being the rotational correlation time. When te � tr dominates the nuclear relaxation and the experimental results can be readily explained by Redfield theory. When te << tr current theory predicts the nuclear T1 values to get longer as H0 decreases. This is not observed experimentally. This can only be explained by using non-Redfield relaxation theory and by assuming the spacings of the electron-nuclear spin energy levels are not dominated by H0. It is shown that, although the trace of the zero-field splitting tensor is zero TrD = 0 because TrD is averaged by tr when te < tr the value of Dzz is important in determining the energy-level spacings. By this approach the frequency dependence can be explained. Experimentally, it is shown that a Phase Alternating Pulse Sequence (PAPS) is required to measure T1. The problem originates from interference from transverse magnetization. A density matrix theory of the PAPS sequence is presented.

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