title: Target structure induced suppression of the ionization cross section for very low energy antiproton-hydrogen collisions.
abstract: Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.
authors.affiliation: Department of Physics and Astronomy, University of Aarhus, DK 8000, Denmark. hk@phys.au.dk
authors.forename: H
authors.initials: H
authors.lastname: Knudsen
authors.forename: H A
authors.initials: HA
authors.lastname: Torii
authors.forename: M
authors.initials: M
authors.lastname: Charlton
authors.forename: Y
authors.initials: Y
authors.lastname: Enomoto
authors.forename: I
authors.initials: I
authors.lastname: Georgescu
authors.forename: C A
authors.initials: CA
authors.lastname: Hunniford
authors.forename: C H
authors.initials: CH
authors.lastname: Kim
authors.forename: Y
authors.initials: Y
authors.lastname: Kanai
authors.forename: H-P E
authors.initials: HP
authors.lastname: Kristiansen
authors.forename: N
authors.initials: N
authors.lastname: Kuroda
authors.forename: M D
authors.initials: MD
authors.lastname: Lund
authors.forename: R W
authors.initials: RW
authors.lastname: McCullough
authors.forename: K
authors.initials: K
authors.lastname: Tökesi
authors.forename: U I
authors.initials: UI
authors.lastname: Uggerhøj
authors.forename: Y
authors.initials: Y
authors.lastname: Yamazaki