NUCLEAR MAGNETIC RELAXATION IN GAS MIXTURES

1962 ◽  
Vol 40 (8) ◽  
pp. 1027-1035 ◽  
Author(s):  
D. Llewelyn Williams

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.

1969 ◽  
Vol 47 (13) ◽  
pp. 1355-1369 ◽  
Author(s):  
Krovvidi Lalita ◽  
Myer Bloom ◽  
John D. Noble

The proton spin–lattice relaxation time T1 in normal H2 gas has been measured as a function of temperature between 293 °K and 738 °K and pressure between 7 and 135 atm. These data and previous measurements at lower temperatures are analyzed in terms of a generalized theory which takes into account the influence of collisions which change the rotational quantum number J as well as those which only change MJ. It is concluded that collisions which change J play an important role even at temperatures as low as 200 °K. The relative importance of different types of inelastic collisions which give rise to changes in J is discussed. Some preliminary results of the radial dependence of the anisotropic H2–H2 interaction are given, but more accurate measurements of T1 as a function of ortho-H2 below room temperature are required to make a definitive interpretation.


1993 ◽  
Vol 48 (5-6) ◽  
pp. 713-719
Author(s):  
K. Venu ◽  
V. S. S. Sastry

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.


1991 ◽  
Vol 46 (8) ◽  
pp. 697-699
Author(s):  
F. Milia ◽  
Y. Bakopoulos ◽  
Lj. Miljkovic

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


1995 ◽  
Vol 50 (8) ◽  
pp. 737-741 ◽  
Author(s):  
Noriaki Okubo ◽  
Mutsuo Igarashi ◽  
Ryozo Yoshizaki

Abstract The 81Br nuclear spin-lattice relaxation time in AlBr3 has been measured between 8 K and room temperature. The result is analyzed using the theory of the Raman process based on covalency. A Debye temperature of 67.6 K and covalency of 0.070 and 0.072 for terminal and 0.022 for bridging bonds are obtained. The correspondence of the latter values to those obtained from the NQR frequencies is low, in contrast to the previously examined compounds.


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