Quasi-elastic neutron scattering study of benzene adsorbed in ZSM-5

Abstract

The quasi-elastic neutron scattering of benzene adsorbed at two different loadings in H-ZSM-5 has been studied in the temperature range 90–400 K. The translational motion is too slow to be observed on the timescale of the experimental so that only the rotational motions can be characterized. The model of uniaxial rotation in an N-fold cosine potential is used to interpret the experimental data. On decreasing temperature, there is a progressive blocking of the molecules for both loadings but the amplitude of motion is more restricted at higher loading, at the same temperature, indicating benzene–benzene interactions. Isotropic spherical rotation is not observed, in agreement with n.m.r. results, and the C₆ uniaxial rotation is as fast as in the liquid, with a correlation time τ= 3.2 × 10^–12 s at 300 K.