Low-temperature motion of the scandium bimetal in endofullerene Sc 2 @C 80 (CH 2 Ph).

The spin decoherence of the scandium bimetal in Sc 2 @C 80 (CH 2 Ph) is studied at low temperatures (20-120 K) by the electron spin echo technique. The correlation between the magnetic quantum number m of the total spin state of the scandium nuclei j and the decay rates is established. For the total spin j = 5, a decrease of the phase relaxation time by a factor of two is observed by changing the transition from m = -1 to m = +1 and m = -3 at 120 K. The observed results are rationalized in the framework of the rotational diffusion of the endohedral fragment in the fullerene cage. It is found that the characteristic rotation time is of the order of a microsecond at 100 K and increases at lower temperatures.