Nuclear magnetic resonance proton dipolar order relaxation in the selectively deuterated nematicpara-azoxyanizole

Autor:	Daniel J. Pusiol, R. C. Zamar, O. Mensio, S. Becker
Rok vydání:	1999
Předmět:	Larmor precession Zeeman effect Proton Spins Chemistry Relaxation (NMR) General Physics and Astronomy Thermotropic crystal symbols.namesake Nuclear magnetic resonance Liquid crystal Residual dipolar coupling symbols Physical and Theoretical Chemistry
Zdroj:	The Journal of Chemical Physics. 110:8155-8160
ISSN:	1089-7690 0021-9606
Popis:	Larmor frequency dependent measurements of Zeeman (T1Z) and dipolar order (T1D) relaxation times provide experimental information on the molecular dynamics in liquid crystals. However, at present, a comprehensive theoretical expression relating T1D with the spectral densities of the molecular motions is not available for liquid crystals. In fact, recent relaxation studies in nematic thermotropic liquid crystals have shown that the traditional model of isolated phenyl proton pairs predicts a relaxation of the dipolar order noticeably slower than the observed one. In this work we show that the failure cannot be assigned exclusively to the assumption of isolated spin-pairs. With this aim, we study the dipolar order relaxation in the nematic PAAd6 (methyl deuterated para-azoxyanizole). After calculating a generalized expression for T1D valid for an arbitrary number of spins, we found that the contributions from multispin interactions and correlations are negligible. This means that, from the point of view of ...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::e375431be9aa1ec87d64e5a247ae4c24 https://doi.org/10.1063/1.478718 Zobrazit plný text záznamu