1. A. Rahman, M. J. Mandell andJ. P. McTague:J. Chem. Phys.,64, 1564 (1975).
2. The authors present their results in terms of reduced variables. Here however we have chosen to specialize to the case of Ar, for an easier comparison with the known spectra of this elements in its various states.
3. The author is indebted to Prof.Rahman for having kindly supplied him with the detailed results about the said radial distribution.
4. S. Franchetti:Nuovo Cimento B,26, 507 (1975).
5. J. B. Pendry: inLow Energy Electron Diffraction (London, New York, N. Y., 1974), p. 200.