Triple coincidence (e,gamma2e) experiment for simultaneous electron impact ionization excitation of helium.
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.
Sakhelashvili
G
G
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
Dorn
A
A
Höhr
C
C
Ullrich
J
J
Kheifets
A S
AS
Lower
J
J
Bartschat
K
K