β Scribed by Roger H. Newman; Sally J. Davenport
No coin nor oath required. For personal study only.
spin-lattice relaxation time constants (TV) have been found to range over more than an order of magnitude for coals of different rank'-'.
Proposed relaxation mechanisms have included spin diffusion to paramagnetic centreslm3 or to rotating methyl groups5, and penetration of molecular oxygen into the coal'.
Evidence is now presented for a large contribution from spin-relaxation processes in adsorbed moisture. Values of T1 were measured indirectly from 50.3 MHz 13C CP/MAS n.m.r. spectra by varying the recovery delay inserted after each 5 ms data acquisition period. Signal heights were monitored for peaks at 6 = 30 and 130 ppm (assigned to methylene groups and aromatic rings respectively). The signal recovery curves were approximately exponential.
π SIMILAR VOLUMES
New symmetry-adapted autocorrelation functions are used in A 1/2 Γ 3p 5 (N 0 1)g 4 α 2 b 06 , [3] the theoretical description of the nuclear magnetic dipole-dipole relaxation in molecular crystals. They are obtained in the model frame that a molecule rotates by means of the finite angular jumps N is