Quasielastic Neutron Scattering to Determine Self-Diffusion Constants in Liquid p-Azoxyanisol

Abstract

Abstract Quasielasiic scattering experiments on nematic p-azoxyanisol have been performed at relatively small scattering vectors (K<0.3Å−1) and with a correspondingly high energy resolution (4·10−7 eV), using a backscattering neutron spectometer. The observed quasielastic width can be interpreted in terms of self-diffusion, and the resulting diffusion constant (D = 4, 1.10−6 cm2/sec) agrees quite well with results from tracer experiments (Yun and Fredrickson). The quasielastic width measured by several other authors at relatively large K-values (several Å−1) should be interpreted by rotational motions of the molecule with an estimated rotational diffusion constant of Dr = 1010 .. 10 11 sec−1.