The structure factor for liquid nitrogen and liquid oxygen from neutron scattering studies

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Abstract
The structure factor, S(Q), has been measured for liquid nitrogen at 77 K and liquid oxygen at 84 K by neutron diffraction over a range of momentum transfer, Q, from 0·3 to 7·3 Å-1. In the case of oxygen a correction for magnetic scattering has been included. The liquid structure factor for nitrogen compares well with that obtained from X-ray diffraction measurements but there are significant discrepancies in the case of oxygen. These may be partially attributed to uncertainty in the form factor for paramagnetic scattering. The data have been analysed in terms of several different models for the orientational correlation between neighbouring molecules. The results are particularly sensitive to uncertainties in the absolute normalization of the data, the inter-nuclear distance for the molecular structure and Placzek corrections; the effect of these errors is considered in detail. It is shown that some form of orientation correlation must exist but its precise nature could not be obtained from the present data.