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Proton spin-lattice relaxation times have been measured in the gaseous mixtures CH4-N2 and CH4-C02 as a function of density and composition in the temperature region 300-600 K. The values of T , / p extrapolated to 1 0 0 z N2 and CO, respectively were found to be proportional to T-" where 12 = 0.87 + 0.14 for CH4-N, and tl = 0.91 f 0.10 for CH4-CO,. It is not possible to fit these data using a hard sphere potential for the isotropic part. Using the BloomOppenheim theory and assuming that the correlation time of the spin-rotation interaction can be approximated by the average lifetime of a molecule in the given J state, it is shown that the above temperature dependence can be fitted by a 12-6 Lennard-Jones potential combined with an appropriate anisotropic potential. We have obtained the strengths of the repulsive and attractive terms in the anisotropic potential by a least squares fit of the data. Using the known values of the quadrupole moments of N, and CO,, the octopole moment of CH4 has been obtained.On a mesure les temps de relaxation spin-reseau dans des melanges gazeux CH4-N2 et CH4-CO,, en fonction de la densite et de la composition du melange, dans la region de temperature 300-600 K. Pour le rapport T , / p extrapole a 100z N2 et CO, respectivement, on a trouvt des valeurs proportionnelles a T-" avec t~ = 0.87 + 0.14 pour CH4-N2 et n = 0.91 f 0.10 pour CH,-CO,. I1 n'est pas possible de retrouver ces valeurs a partir d'un potentiel de sphkre dure pour la partie isotrope. En utilisant la theorie Bloom-Oppenheim et en supposant qu'on peut prendre comme valeur approximative du temps de correlation de I'interaction spin-rotation la vie moyenne d'une molecule dans I'etat Jconsidere, on montre que la variation en fonction de la temperature rapportee ci-dessus peut &re expliquee par un potentiel de Lennard-Jones 12-6 combine avec un potentiel anisotrope approprie. Nous avons obtenu les forces des termes de repulsion et d'attraction dans le potentiel anisotrope, en ajustant les donnees par la methode des moindres carres. En utilisant les valeurs connues des moments quadrupolaires de N, et CO,, on a obtenu le moment octupolaire de CH,.[Traduit par le journal]Can.

Proton and fluorine spin–lattice relaxation times per unit density, T1/ρ, in pure gases CH4, CF4, and SiF4 are experimentally found to be proportional to T−1.5 where T is the temperature. Using either a hard sphere or a 12–6 Lennard–Jones potential for the isotropic part of the intramolecular potential, it is shown here that these data can be analyzed to obtain information on the anisotropic part of the potential in these systems. The analysis is made within the framework of the Bloom–Oppenheim theory, assuming that the correlation time of the spin–rotation interaction can be approximated by the average lifetime of a molecule in the given J state. From the strength of the attractive term in the anisotropic potential, the octopole moments of all the three molecules are obtained. These values are comparable with the values reported earlier based on other techniques for CH4 and CF4 in case of the Lennard–Jones model. The octopole moments of CH4 and CF4 obtained from the hard sphere model are smaller by 25% than those from the Lennard–Jones model. For SiF4, we obtain values of 4.14 × 10−34 e.s.u. cm3 and 5.3 × 10−34 e.s.u. cm3, as the octopole moments from the Lennard–Jones and the hard sphere models respectively and no other value exists in the literature.

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The last two decades have seen the emergence of a specialized fishing fleet of small-scale fishermen that operate over large swathes of the central-western Indian Ocean. This fleet undertakes extended voyages of 30-45 days in order to conserve fuel, and targets specific varieties of pelagic fish. In order to improve their sustainability as well as to cut down their costs, these fishers are in the process of adapting solar energy for their lighting, communications and other on-board needs. This paper documents the initial iterations of the adoption process, which holds significant promise for the future in terms of energy & cost savings and for the promotion of sustainable fishing operations.