SEARCH

SEARCH BY CITATION

Keywords:

  • 1H;
  • 2H MAS NMR;
  • T1 times;
  • effects of spinning rates on T1 relaxation

Abstract

The inversion-recovery 1H, 2H time measurements in methanol, methanol-d4, and D2O, placed into standard 4 mm and 2.5 mm MAS NMR rotors show the strong spinning effects. The spin-lattice relaxation follows an exponential in the static samples and deviates from the exponential or transforms to a bi-exponential in the spinning samples. Fast relaxing components in spinning liquids are characterized by 1H, 2H T1 times between 0.1 and 0.2 s, while relaxation times of slowly relaxing domains are close to those (or higher) measured in static experiments. In the absence of oxygen, the relaxation is again exponential. This phenomenon is not artifact and explained by the centrifugal force resulting in accumulation of oxygen at an inverted conical liquid surface at spinning. The oxygen-enriched part of liquids relaxes by the paramagnetic mechanism to show the 1H, 2H T1(short) time components. © 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part A 40A: 186–191, 2012.