NMR relaxation study of molecular motions between unequal potential wells in solid trans, trans- muconodinitrile

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Publication Type Journal Article
School or College College of Science
Department Physics
Creator Ailion, David Charles
Other Author Polak, Micha
Title NMR relaxation study of molecular motions between unequal potential wells in solid trans, trans- muconodinitrile
Date 1977
Description We report observations of extremely unusual proton NMR relaxation rates in solid trans, transmuconodinitrile (TMD, N=C-CH = CH-CH = CH-C = N). In particular we measured, over the temperature range 77-423 °K, proton dipolar relaxation times Tw and spin lattice relaxation times Tt (at 24 and 58 MHz). The relaxation pattern is characterized by the following features: (a) very long motional r, and F 1 0 even at their respective minima, (b) no detectable motional narrowing of the line even at the Tl c minimum, (c) unequal slopes at temperatures below and above the minimum of T, (and r , 0 ) vs 1/7". and (d) significant deviations from the usual linear dependence on resonance frequency of the values of the relaxation times at their respective minima. We extended an earlier NMR theory to the case of spin lattice relaxation due to molecular reorientations between the extremely unequal potential energy wells of TMD. We were able to explain all features of the above data in terms of this theory. By comparing our data to the results of several calculations of intermolecular potential energy which used different interatomic force parameters, we were able to rule out some of these, thereby determining the best choice for the parameters in this crystal. The detailed structure of this potential profile (i.e., relative depths of the wells and energy barriers hindering rotation) was then determined from the Tt and Tw data. We thus have observed and characterized in TMD a low concentration of orientational defects which occur when a molecule occupies a higher energy well. Our observations are probably the first of such extreme NMR relaxation effects due to motions between significantly inequivalent sites.
Type Text
Publisher American Institute of Physics (AIP)
Volume 67
Issue 6
First Page 3029
Last Page 3039
Subject NMR; Nuclear magnetic resonance; Lattices; Relaxation time
Subject LCSH Nuclear magnetic resonance; Nuclear physics
Dissertation Institution University of Utah
Language eng
Bibliographic Citation Polak, M. & Ailion, D. C. (1977) NMR relaxation study of molecular motions between unequal potential wells in solid trans, trans- muconodinitrile. Journal of Chemical Physics, 67(6), 3029-39.
Rights Management (c)American Institute of Physics. The following article appeared in Polak, M. & Ailion, D. C., Journal of Chemical Physics. 67(6) 1977 and may be found at http://link.aip.org/link/?JCPSA6/67/3029/1
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Identifier ir-main,5014
ARK ark:/87278/s68p6j2p
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Date Created 2012-06-13
Date Modified 2021-05-06
ID 706034
Reference URL https://collections.lib.utah.edu/ark:/87278/s68p6j2p
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