Neutron slow--------scattering from chemically

An adequate theoretical basis for the calculation of slow neutron scattering from chemically bound systems exists in the pseudo-potential approximation introduced by Fermi in 1937 [1]. The fundamental cross section of interest for neutron thermalization is the differential cross section g(Eo,E,6) for energy transfer Eq- E with scattering through an angle 0 in the laboratory system. The calculation of this cross section, even in the pseudo-potential approximation, depends on the detailed dynamics of the atomic motion in the moderator. The dynamics of atomic motion in crystals and liquids is complicated and not as yet known in detail. The direction of most fundamental interest, therefore, is to determine these dynamical properties from experimental measurements of slow neutron scattering. 

A. Theoretical basis. The theoretical basis for the calculation of slow neutron scattering from chemically bound systems is the pseudo-potential approximation. This approximation can be derived [13] by replacing the strong, short-range /S-wave interaction between neutron and nucleus by a boundary condition on the wave function at small neutron-nucleus separation. This corresponds to replacing the actual interaction by a pseudo-potential interaction... 

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