1H Spin-Lattice Relaxation Times of Water, Methanol, and Ethanol under Sub- and Supercritical Conditions

1H NMR spin-lattice relaxation times (T1) of water, methanol, and ethanol (abbreviated as W.M.E) were measured in the range of 25 to 400 °C at 30, 20, and 20 Mpa, respectively by using high-pressure NMR. It was found that the T1 values for each group of W.M.E increase with an increase in temperature up to around 220, 160, and 170 °C, and that above these temperatures, the T1 values decrease and approach a constant value at 300, 200, and 220 °C, respectively. It is explained that the spin-lattice relaxation (SLR) processes are dominated by the dipole-dipole (DD) mechanism at lower temperature and by the spin-rotation (SR) mechanism at higher temperatures. The reasons that the T1 values are nearly constant are supposed.

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