Small-angle neutron scattering model fitting

Fig. 3 Small angle neutron (squares) and X-ray (triangles) scattering curves given as I q)/cm versus The symbols correspond to the experimental data and the solid lines represent fits with a form factor model for monodisperse oblate ellipsoids...

A more recent measurement for N2 gas at 100 bar[5] is shown in Figure 1 with a fit to the intra-molecular scattering superimposed. Figure 2 shows the inter-molecular cross-section with a fit based on the Kihara potential [6]. Since the N2 molecule has a small anisotropy, very precise measurements are required to discriminate between different potential forms and this situation is similar to that reflected in the liquid studies presented in the previous chapter. A similar treatment of neutron measurements [7] on SFe gas, however, does reveal some interesting facts about the parameterization of the potential and discriminates between dif ferent models. It therefore seems that neutron diffraction studies of the gas phase can yield useful supplementary information about angle-averaged interaction potentials. In this sense B2((1,T) can be seen as an extension of the conventional second virial coefficient B2(T). At present, these two molecules (N2 and SFg) are the only ones that have been studied in detail but the method clearly has scope for wider applications. 

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