A new type of sample tube for reducing convection effects in PGSE-NMR measurements of self-diffusion coefficients of liquid samples |
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Authors: | Hayamizu Kikuko Price William S |
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Institution: | National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Center 5, Tsukuba 305-8565, Japan. hayamizu.k@aist.go.jp |
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Abstract: | Pulsed gradient spin-echo (PGSE) NMR measurements of the self-diffusion coefficients of low viscosity liquids are greatly hampered by the effects of convection especially away from ambient temperature. Here we report on a new NMR tube designed to minimize the deleterious effects of convection. In this tube, which derives from a Shigemi symmetrical NMR tube, the sample is contained in an annulus formed from a concentric cylinder of susceptibility matched glass. The performance of this tube was demonstrated by conducting measurements on the electrochemically important LiN(SO3CF3)2 (LiTFSI)-diglyme (DG) system. Calibrations were first made using DG at column heights of 2, 3, and 4-mm in the temperature range between -40 and 100 degrees C. Measurements of the diffusion coefficients of the lithium, anion, and DG were then performed to probe the solvent-ion and ion-ion interactions in the DG doped with LiTFSI. Changes in the 1H, 7Li, and 19F PGSE-NMR attenuation curves at -40 degrees C provided clear evidence of interactions between the DG and lithium ion. |
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Keywords: | Author Keywords: Convection Diffusion Ion– ion and ion– solvent interactions Low viscosity liquid NMR tube PGSE-NMR |
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