ROTATIONAL STATE J = 1 IN ORIENTATIONALLY DISORDERED AND ORDERED SOLID HYDROGEN

The rotational transition J=1→J=0 in solid H2 was measured by incoherent neutron scattering. Results are presented for the mean energy of this transition as a function of the ortho concentration at temperatures 4.2 and 1.2 K. The data at 4.2 K are compared with theoretical calculations resolving a discrepancy between these calculations and previous experiments. At 1.2 K and high ortho concentrations, our data cannot be interpeted in terms of an orientationally ordered fcc phase as would be expected. This observation is discussed in terms of an orientationally ordered hcp phase originating perhaps from the effects of internal strains. © 1978 Springer-Verlag.