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

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

Revealing the non-

The correlated Tunneling Transfer Ionization (TuTI) channel in fast 4-body processes \ab{p} +\chem{He}\rightarrow\chem{H^0}+\chem{He^{2+}}+\ab{e} is utilized to probe the highly correlated asymptotic parts of the \chem{He} ground-state momentum space wave function. In this reaction, predominantly at large nuclear impact parameters, one electron in the \chem{He} ground state is captured by the proton by tunneling through the two-center barrier when electron and proton velocity vectors resonantly match. The measured 3-particle final-state momentum distributions show characteristic features that we trace back to the highly correlated non-s2 components of the \chem{He} ground-state momentum wave function. This conclusion is supported by a simple heuristic model

Fully differential cross sections for photo double ionization of fixed-in-space D2. Phys. Rev. Lett. submitted for publication.

Abstract We report the first kinematically complete study of the four-body fragmentation of the D 2 molecule following absorption of a single photon. For equal energy sharing of the two electrons and a

Fully differential cross sections for photo-double-ionization of D{sub 2}

We report the first kinematically complete study of the four-body fragmentation of the D2 molecule following absorption of a single photon. For equal energy sharing of the two electrons and a photon energy of 75.5 eV, we observed the relaxation of one of the selection rules valid for He photo-double ionization and a strong dependence of the electron angular distribution on the orientation of the molecular axis. This effect is reproduced by a model in which a pair of photoionization amplitudes is introduced for the light polarization parallel and perpendicular to the molecular axis

Fully differential cross sections for photo double ionization of fixed-in-space D2. Phys. Rev. Lett. submitted for publication.

We report the first kinematically complete study of the four-body fragmentation of the D 2 molecule following absorption of a single photon. For equal energy sharing of the two electrons and a photon energy of 75.5 eV, we observed the relaxation of one of the selection rules valid for He photo-doubleionization and a strong dependence of the electron angular distribution on the orientation of the molecular axis. This effect is reproduced by a model in which a pair of photoionization amplitudes is introduced for the light polarization parallel and perpendicular to the molecular axis. DOI: 10.1103/PhysRevLett.92.163001 PACS numbers: 33.60.Cv, 33.80.Eh, 31.15.Ar The simultaneous ejection of two electrons by the absorption of a single photon (photo-double-ionization or PDI) is a paradigm in the study of the dynamics of electron-electron correlation. However, only the simplest process of this kind, i.e., PDI of helium, is substantially well understood (see Pioneering experiments on PDI of H 2 measured the ion fragments and yielded the total cross section and the ion angular distribution ([2,3]). More recently, two-electron coincidence (; 2e) experiments (no ion detection) ([4 -7]) and one-electron-two-ion coincidence measurements [8] became feasible. The (; 2e) results revealed surprising similarity of the electron angular distributions for He and D 2 . For He, at energies up to 100 eV above threshold, these angular distributions (fully differential cross sections-FDCS) are governed by the final state repulsion of the two electrons and selection rules resulting from the 1 P 0 symmetry of the final two-electron state Despite this similarity of the PDI of He and H 2 some selection rules that exclude certain escape geometries are relaxed for H 2 ([9,11]). Primarily, this relaxation stems from the loss of a fixed angular momentum for the photoelectron pair; i.e., the electronic continuum wave function does not have pure P symmetry. The molecular ground state contains high angular momentum components and electron scattering by the nuclei during escape can mix angular momenta. In helium, for equal energy electrons, the cross section is zero on a cone 2 180 ÿ 1 , where 1;2 are the polar angles of electrons 1 and 2 with respect to the polarization axis (see selection rule F i