title: Resonant scattering of positronium in collision with CO2.
abstract: The total cross sections of positronium (Ps) scattering from a carbon-dioxide molecule have been measured over the range (7-400) eV incident-Ps energy. For the first time in Ps collisions, a resonantlike structure is observed. For the present target, it occurs around 9.5 eV followed by a broader peak at ∼60 eV. Following Brawley et al. [Science 330, 789 (2010)] who have observed similarities between the total cross sections of positronium and of electrons incident upon a given target at the same velocity, a corresponding comparison is made for CO2. The comparison suggests that the former peak corresponds to the well-known 2Π(u) shape resonance which occurs for electrons at an incident velocity of 0.5 a.u. Further features are discussed and theoretical input is sought.
authors.affiliation: UCL Department of Physics and Astronomy, University College London, London, United Kingdom.
authors.forename: S J
authors.initials: SJ
authors.lastname: Brawley
authors.forename: A I
authors.initials: AI
authors.lastname: Williams
authors.forename: M
authors.initials: M
authors.lastname: Shipman
authors.forename: G
authors.initials: G
authors.lastname: Laricchia