Planar central configurations of four different masses are analyzed theoretically and computed numerically. We follow Dziobek's approach to four-body central configurations with a straightforward implicit (in the masses and distances) method of our own in which the fundamental quantities are each the quotient of a directed area divided by the corresponding mass. We apply a new simple numerical algorithm to construct general fourbody central configurations. We use this tool to obtain new properties of the symmetric and non-symmetric central configurations. The explicit continuous connection between threebody and four-body central configurations where one of the four masses approaches zero is clarified. Some cases of coorbital 1 + 3 problems are also considered.

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The dynamic structure factor for nitrogen gas has been measured for seven densities along the room temperature isotherm, for values of the momentum transfer (hq) of 0-4<:q< 3.2 •-1. In this paper the experimental details are given and a full analysis of the integrated time-of-flight spectra. The resulting static structure factors are compared with recent computer simulations using a site-site Lennard-Jones potential plus quadrupole terms. There is good overall agreement in this q range at all densities. This comparison also indicates reasonable agreement in r-space in the nearest neighbour range but some improvements may be required at greater distances.

For pt.I see Mol. Phys., vol.53, p.389 (1984). Neutron scattering measurements of the dynamic structure factor for dense nitrogen gas have been reported in part 1. The authors carried out computer simulations of dense nitrogen gas at room temperature, for densities between 7.1 and 12.1 molecules nm-3, to obtain a prediction for the dynamic structure factor. Compared to the previous experimental results the simulation data showed generally good agreement except for in the ranges (Q<1 AA-1; omega <3 ps-1) and (Q>2 AA-1; omega >10 ps-1), where the simulated data fell below the experimental data. These observations probably indicate deficiencies in the intermolecular potential employed in the simulation over longer ranges ( approximately 10 AA), and also for fast impacts (<10-13 s).