A procedure to determine Dyson orbitals from electron momentum spectroscopy: application to 1,2-Propadiene, 1,3-Butadiene, Cyclopropane and [1.1.1]Propellane

We employ a numerical inverse method of extracting the target-ion overlap, or normalised Dyson orbital, directly from experimental electron momentum spectroscopy data by using a quantum- mechanically constrained statistical fitting procedure. This method is used in conjunction with the previously verified, for molecular targets, plane wave impulse approximation (PWIA) reaction model. The present procedure was applied to previously measured momentum distributions (MDs) for the 2e' and 1e' valence orbitals of cyclopropane, the 7ag orbital of trans 1,3-butadiene, the 2e orbital of 1,2-propadiene and the 3a'1 orbital of [1.1.1]propellane. We note that this is the first extensive application of the present method to organic molecular systems. In each case the derived normalised Dyson orbital provided a superior representation of the experimental MD than did the corresponding Hartree-Fock orbital. The ramifications of this result are discussed in the text. Copyright (1998) CSIRO Australia