TEMPERATURE-DEPENDENT SPECTRAL SPIN-DIFFUSION IN SOLID-STATE DEUTERONMAGNETIC-RESONANCE

The polarization transfer from the para to the ortho/meta deuterons wa s investigated in a single crystal of perdeuterated biphenyl, C12D10. It is demonstrated that this process is due to spin diffusion via dipo lar coupling. We found that in the range from 290 to 315 K it is stron gly dependent on the temperature. The apparent activation energy of ab out 75 kJ/mol is the same as that of the known 180 degrees flips of ph enyl rings about the long molecular axis. As an explanation of the obs erved temperature dependence of the spin diffusion we discuss an excha nge broadening of the relevant zero-quantum line caused by the 180 deg rees flips.