Abrupt Rise of the Longitudinal Recoil Ion Momentum Distribution for Ionizing Collisions

We report on the experimental observation of an abrupt rise in the longitudinal momentum distribution of recoil ions created in proton helium collision. The details of this structure can be related to electrons traveling with the velocity of the projectile [electron capture to the continuum (ECC)]. The longitudinal as well as the transverse distribution of the recoil ions can be explained as a continuation of the momentum distribution from ions resulting from electron capture illustrating the smooth transition from the capture to bound states of the projectile to the ECC.Fil: Weber, Th.. Institut für Kernphysik; AlemaniaFil: Khayyat, Kh.. Institut für Kernphysik; AlemaniaFil: Dörner, R.. Universität Freiburg; AlemaniaFil: Rodríguez Chariarse, Vladimir Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Mergel, V.. Institut für Kernphysik; AlemaniaFil: Jagutzk, O.. Institut für Kernphysik; AlemaniaFil: Schmidt, L.. Institut für Kernphysik,; AlemaniaFil: Müller, K. A.. Institut für Kernphysik; AlemaniaFil: Afaneh, F.. Institut für Kernphysik; AlemaniaFil: Gonzalez, A.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Schmidt-Böcking, H.. Institut für Kernphysik; Alemani

Energy-Loss Measurements for Single and Multiple Ionization of Argon by Positron Impact

Experimental data, as a function of projectile energy loss, are presented for single, double and triple ionization of argon by 750 eV positrons. These differential ionization yields are for positrons scattered into a forward cone of angles between O° and 17° and for energy losses up to 85% of the initial energy. The single ionization data are shown to be in good agreement with distorted wave Born calculations. For the angular range investigated the percentage of double ionization is found to increase rapidly for the first 80 eV of energy loss. The ratio then slowly approaches a constant value that is in good agreement with the ratios of total cross sections for photoionization of the M shell. The present energy-loss data also demonstrate the importance of outer versus inner-shell ionization in the double and triple ionization channels

Separation of Photoabsorption and Compton Scattering Contributionsto He Single and Double Ionization

We have experimentally separated the contributions of photoabsorption and Compton scattering to He single and double ionization for high-energy photon impact by measuring the full momentum vector of the recoiling He1+,2+ ions. For recoil ions following photoabsorption large momenta and a distinct dipole emission pattern are observed. The ions produced by Compton scattering show small momenta. For the ratio of double to single ionization we find (1.22±0.06)% at 8.8+1.5−1.65 keV for Compton scattering and (1.72±0.12)% at 7.0+2.1−1.6 keV for photoabsorption. We compare our data with recent theories

Cross-section ratio of double to single ionization of helium by Compton scattering of 40–100-keV X-rays

We have measured the ratio of cross sections for double to single ionization of helium by Compton scattering, RC=σ++C/σ+C, at photon energies of 40, 80, and 100 keV using cold target recoil-ion momentum spectroscopy. Comparison with calculations involving highly correlated initial states and approximate final states with and without final-state correlations, represented by 3C and 2C wave functions respectively, shows that the influence of final-state correlations persists to very high photon energies. A comparison with recent charged-particle data is made