Rotational States and Self-Dilution vs. Translational Disorder in Plastic Neopentane

Neutron diffraction experiments performed on orientationally disordered neopentane single crystals display anomalous translational disorder. This result is discussed using a new model in which reorientating molecules behave as long-lived rotational states which act as static spherical impurities. Very low concentrations of the virtual impurities are sufficient to reproduce the data.