The interpretation of binary (e, 2e) spectroscopy using spin-coupled theory

We discuss the possible interpretation of the (e, 2e) scattering technique (electron momentum spectroscopy) in terms of spin-coupled wave functions. The spin-coupled method is a modern valence bond approach which is based on a simple picture of singly occupied orbitais. In general these are highly localized, unlike their molecular orbital theory counterparts, and this has important consequences for the form of the momentum space orbitais to which the experimental differential cross-sections can be related. We compare spin-coupled and molecular orbital electron densities for individual orbitais of LiH, NH, CH₂CHF and CH₂CHCl, both in momentum space and in the more familiar position space representation. Finally, we comment briefly on the possible significance of this new approach for resolving the present discrepancies between theory and experiment for NH₃, H₂O and HF.