Neutron diffraction experiments on powders are used to investigate the quantum mechanical behaviour of uniaxial rotators, i.e. NH 3 -molecules in Ni(NH 3 ) 6 (PF 6 ) 2 , Co(NH 3 ) 6 (PF 6 ) 2 and Ni(NH 3 ) 6 I 2 . A diffuse temperature dependent component of the total scattering, modulated sin Qr H - /Qr H - H , is observed at a temperature of 20 K and below. This observation is due to the fact, that on cooling the sample to kT B (rotational constant) the rotational ground state is strongly populated. The ground state of a uniaxial free rotator, however, is completely polarized. As a consequence the scattering of those NH 3 groups being in the ground state becomes coherent and is observable in diffraction experiments.