A proton FFT study of the aromatic and alkyl motions in the liquid crystal CBOOA: Orientational order fluctuations in the isotropic phase

1976 ◽  
Vol 54 (22) ◽  
pp. 2282-2286 ◽  
Author(s):  
J. J. Visintainer ◽  
E. Bock ◽  
Ronald Y. Dong ◽  
E. Tomchuk
Keyword(s):  
Liquid Crystal ◽  
Critical Temperature ◽  
Orientational Order ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Isotropic Phase ◽  
Spin Lattice ◽  
Temperature Dependences

Proton line shapes and spin–lattice relaxation were studied in the isotropic phase of the liquid crystal n-p-cyanobenzylidene-p-n-octyloxyaniline (CBOOA) using Fast Fourier Transform (FFT) spectroscopy. The proton spin–lattice relaxation time T1 above the nematic–isotropic phase transition was measured, at several Larmor frequencies, for the resolved peaks in the FFT spectra. The critical temperature dependences of (T1)cf, the T1, due to collective order fluctuations, are thus studied for the aromatic and the alkyl proton groups. The critical temperature behavior of CBOOA is compared with the predictions of the model based on short-range nematic orientational order fluctuations.

Proton Spin-Lattice Relaxation Study of Order Fluctuations Above The Smectic A-Isotropic Transition in a Liquid Crystal

1974 ◽  
Vol 52 (14) ◽  
pp. 1331-1335 ◽  
Author(s):  
Ronald Y. Dong ◽  
M. Wiszniewska ◽  
E. Tomchuk ◽  
E. Bock
Keyword(s):  
Relaxation Time ◽  
Liquid Crystal ◽  
Effective Viscosity ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Isotropic Phase ◽  
Spin Lattice ◽  
Smectic A

The proton spin-lattice relaxation time T1 in the isotropic phase of the smectic A liquid crystal diethylazoxybenzoate was measured at several Larmor frequencies in the range from 5 to 60 MHz. The frequency dependent T1 at 25 °C above the smectic A-isotropic phase transition (Tc) is attributed to molecular diffusion. The critical temperature dependent (T1)cf, the spin-lattice relaxation time due to critical order fluctuations, at 5 MHz can be understood by assuming that the effective viscosity has a critical temperature behavior just above Tc. It was deduced that the effective viscosity diverges as ξ2 in the mean field approximation, where ξ is a coherence length describing the short range order.

Proton Spin Relaxation Study of Order Fluctuations above the Nematic–Isotropic Transition in the Liquid Crystal MBBA: I. Applicability of BPP Theory

1974 ◽  
Vol 52 (9) ◽  
pp. 766-771 ◽  
Author(s):  
Ronald Y. Dong ◽  
M. Wiszniewska ◽  
E. Tomchuk ◽  
E. Bock
Keyword(s):  
Spin Relaxation ◽  
Orientational Order ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Relaxation Study ◽  
Critical Order

The proton spin-lattice relaxation time T1 was used to study the short range orientational order fluctuations just above the nematic–isotropic transition in p-methoxy benzyli-dene p-n-butylaniline at 14, 11, and 4 MHz. This is made possible by calculating the contribution to the spin relaxation rate due to the molecular self-diffusion, which is known to be effective in relaxing the proton spins. The (T1)ef due to the critical order fluctuations at 4 MHz can be interpreted with the theory of de Gennes but not with the simple Bloembergen–Purcell–Pound theory.

Dispersion of proton spin-lattice relaxation in a cholesteric liquid crystal

1983 ◽  
Vol 44 (10) ◽  
pp. 1179-1184 ◽  
Author(s):  
M. Vilfan ◽  
R. Blinc ◽  
J. Dolinšek ◽  
M. Ipavec ◽  
G. Lahajnar ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Proton Spin Lattice Relaxation in the Dimethylammonium Group

1993 ◽  
Vol 48 (5-6) ◽  
pp. 713-719
Author(s):  
K. Venu ◽  
V. S. S. Sastry
Keyword(s):  
Experimental Data ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Dipolar Interactions ◽  
Spin Temperature ◽  
Spin Lattice ◽  
Molecular Group

Abstract A model for the spin lattice relaxation time of the protons of dimethylammonium in the Redfield limit and common spin temperature approximation is developed. The three fold reorientations of the methyl groups, the rotation of the whole molecular group around its two fold symmetric axis and possible correlations among these motions are considered. The effect of these processes on the dipolar interactions among the protons within the same molecular group is taken into account. The resulting relaxation rate is powder averaged and used to explain the experimental data in literature on [NH2(CH3)2]3Sb2Br9 . The analysis shows that dynamically inequivalent groups exist in this compound and that the effect of proposed correlation among the different motions on the final results is negligible.

NUCLEAR MAGNETIC RELAXATION IN GAS MIXTURES

1962 ◽  
Vol 40 (8) ◽  
pp. 1027-1035 ◽  
Author(s):  
D. Llewelyn Williams
Keyword(s):  
Room Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Gas Molecules ◽  
De Broglie Wavelength ◽  
Diffraction Effects ◽  
Good Agreement

Measurements of the proton spin–lattice relaxation time using pulse techniques have been made on the hydrogen–nitrogen, hydrogen–neon, and hydrogen–helium systems from room temperature to 60° K. The results are in good agreement with the Oppenheim–Bloom theory and illustrate the importance of the radial distribution of the gas molecules and of diffraction effects associated with the de Broglie wavelength.

Surface Induced Spin-Lattice Relaxation of Water in Tricalcium Silicate Gels

1991 ◽  
Vol 46 (8) ◽  
pp. 697-699
Author(s):  
F. Milia ◽  
Y. Bakopoulos ◽  
Lj. Miljkovic
Keyword(s):  
Grain Size ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Tricalcium Silicate ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Water Proton ◽  
Hydration Time ◽  
Spin Lattice ◽  
Stage Process

AbstractThe water proton spin-lattice relaxation time and recovery function of exchangeable water was measured in tricalcium silicate (C3S) gels. The measurements were carried out as a function of the hydration time and grain size. Results show that the hydration of (C3S) is a two stage process. A model is developped

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