Fixed-energy inverse scattering theory has been used to analyze the differential cross sections for the elastic scattering of electrons from water molecules. Both semiclassical (WKB) and fully quantal inversion methods have been used with data taken in the energy range 100–1000 eV. Constrained to be real, the local inversion potentials are found to be energy dependent, a dependence that can be interpreted as the local equivalence of true nonlocality in the actual interaction. Further improvement in fits to the data was found by allowing the interactions to be complex, reflecting the role of coupling of the elastic to nonelastic channels.

• Received 22 October 1993

DOI:https://doi.org/10.1103/PhysRevA.49.3788