Dipolar energy relaxation in a solid mixture of normal and perdeuterated furan

Abstract

Measurements have been made of the dipolar energy relaxation time in the two solid phases of both pure furan C 4H 4O and a mixture of furan in its perdeuterated analog C 4D 4O. Near the melting point, these measurements have revealed very slow motions with a very high activation energy. These motions can be attributed to translational diffusion. The relaxation rate of the dipolar energy does not appear to be influenced by the presence of deuterated molecules. In the low-temperature part of the rotator phase, the relaxation is induced by fast coplanar reorientations of the molecules. Here, the relative variation of the relaxation time of the dipolar energy with respect to the deuteron concentration is opposite to that of the Zeeman relaxation time. In the ordered phase, a slow motion is also detected. We present calculations for the fast-motion case as well as for the slow-motion case which fit satisfactorily the behavior of the dipolar energy relaxation time as a function of the deuterated molecule concentration.