A combined experimental and theoretical study of NMR spin-lattice relaxation times in HD-Ar and D¦2-Ar mixtures

dc.contributor.authorSabzyan, Hasanen
dc.date.accessioned2006-07-28T19:39:01Z
dc.date.available2006-07-28T19:39:01Z
dc.date.issued1997en
dc.date.submitted1997en
dc.description.abstractThe hydrogen-argon system is the preeminent prototype system for the study of atom-diatom interaction potential energy surfaces. The temperature dependence of the NMR spin-lattice relaxation time in the gas phase provides one of the most sensitive tests to the anisotropic part of these potential energy surfaces. The present work consists of a combined experimental and theoretical study of the NMR spin-lattice relaxation times in HD-Ar and D2-Ar mixtures. A gas-handling system and a sample cell have been designed and successfully employed in the experimental part of this study. The spin-lattice relaxation times for the proton and deuteron of HD in HD-Ar mixtures, and for the deuteron of D2 in D2-Ar mixtures have been measured over a wide range of temperatures at several mole fraction and densities. The quality of the results is tested by the analysis of the one-dimensional spectra. The values of the nuclear Overhauser effect (NOE) enhancements for the proton and deuteron of HD in HD-Ar mixtures have been measured; these NOE measurements represent the first such experiments for the gas phase. Theoretical values of the spin-lattice relaxation times and the NOE enhancements have been calculated for the same mixtures using the XC(fit) potential energy surface derived by Bissonnette et al [J. Chem. Phys. 105, 2639-2653, (1996)] for hydrogen-argon systems. A complete analysis of the temperature, field and density dependences of the relaxation times has been carried out for both systems. Two reliable methods have been proposed to compare the theoretical and experimental NMR spin-lattice relaxation times obtained for high temperature equilibrium mixtures of the two parity isomers of the D2-Ar system under the conditions in which separate measurement of their deuteron relaxation times is not possible. The experimental and theoretical results for the HD-Ar system show excellent agreement, but the agreement for the D2-Ar system is relatively good only for higher temperatures. It has been argued that the major source of the difference between the level of agreement for the two systems is due to uncertainties in the anisotropic part of the homonuclear potential energy surface. The accuracy of the anisotropy for the heteronuclear potential energy surface is determined throguh transformation, by the accuracy of the isotropic part of the homonuclear potential, which is usually higher than that of the anisotropic parts. The effects of orbiting resonances and the sensitivity of the NMR cross sections to subtle changes in the potential have been studied. Effects of the non-rigidity of the diatom on the coupling constants, and hence on the NMR relaxation times, have also been studied. Finally, some suggestions for further studies of hydrogen-argon systems have been proposed.en
dc.formatapplication/pdfen
dc.format.extent15470251 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.urihttp://hdl.handle.net/10012/116
dc.language.isoenen
dc.pendingfalseen
dc.publisherUniversity of Waterlooen
dc.rightsCopyright: 1997, Sabzyan, Hasan. All rights reserved.en
dc.subjectHarvested from Collections Canadaen
dc.titleA combined experimental and theoretical study of NMR spin-lattice relaxation times in HD-Ar and D¦2-Ar mixturesen
dc.typeDoctoral Thesisen
uws-etd.degreePh.D.en
uws.peerReviewStatusUnrevieweden
uws.scholarLevelGraduateen
uws.typeOfResourceTexten

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