title: Triple coincidence (e,gamma2e) experiment for simultaneous electron impact ionization excitation of helium.
abstract: Simultaneous ionization and excitation of helium atoms by 500 eV electron impact is observed by a triple coincidence of an ionized slow electron, the recoiling He+ ion, and the radiated vacuum ultraviolet photon (lambda< or =30.4 nm). Kinematically complete differential cross sections are presented for the He+(2p)2P final ionic state, demonstrating the feasibility of a quantum mechanically complete experiment. The experimental data are compared to predictions from state-of-the-art numerical calculations. For large momentum transfers, a first-order treatment of the projectile-target interaction can reproduce the experimental angular dependence, but a second-order treatment is required to obtain consistent magnitudes.
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Sakhelashvili
authors.forename: A
authors.initials: A
authors.lastname: Dorn
authors.forename: C
authors.initials: C
authors.lastname: Höhr
authors.forename: J
authors.initials: J
authors.lastname: Ullrich
authors.forename: A S
authors.initials: AS
authors.lastname: Kheifets
authors.forename: J
authors.initials: J
authors.lastname: Lower
authors.forename: K
authors.initials: K
authors.lastname: Bartschat