Three-centre continuum wavefunction: Application to the (e, 2e) simple ionization of the 1πg, 1πu and 3σu molecular orbitals of CO _2 by fast electron impact

摘要

With the aim of finding an appropriate description of the state of an ejected electron from a linear three-centre molecular target, a wavefunction is constructed in a closed analytical form by solving the Schr?dinger equation of an unbound electron (with wave vector k) in a Coulomb field of three fixed charged nuclei. The model, which is an extension of a two-centre model developed in the past, fulfils the correct boundary conditions asymptotically up to the order O((kr)~(-2)). It is employed, in the frame of a perturbative first Born three-centre procedure, to the determination of the multiply differential cross sections (MDCS) of the (e,2e) simple ionization of the valence 1π_g level of CO_2, for which experimental results were given recently. The ionization of the inner 1π_u and 3σ_u levels of CO_2 are also investigated by this approach. The study of the variation of the MDCS with the direction of the scattered electron and the ejected electron in the case of oriented three-centre targets shows interference patterns similar to those created by the diffraction of light by three apertures.