Neutron scattering study of the reorientational motions in Ni(C₅H₅)₂

Abstract

Incoherent quasi-elastic neutron scattering experiments, using different resolutions, have been performed on polycrystalline samples of nickelocene, Ni(C₅H₅)₂, in the 4–300 K temperature range. It is shown that a unique 2π/5 reorientational jump process of C ₅H₅ rings is taking place below and above the diffuse phase transition at about 200 K. A proton correlation time equal to 4 × 10^-12 s at 300 K, associated with an activation energy of 6·3 kJ mol^-1, is estimated in agreement with literature data. Finally, it is concluded that the asymmetry of the double-well potential function governing the reorientations of C₅H₅ rings, as deduced from heart capacity and Raman results, is too small to be evidenced in neutron scattering experiments.