Differential Cross Sections For Single Ionization Research Articles

Fully differential cross-sections for single ionization of helium by AuQ+ impact

We present fully differential cross-sections (FDCS) within the four-body formalism using the three-body Coulomb wave (4B-3C) for the single ionization of He by 3.6 Mev/amu AuQ+ ions. The purpose of this work is to investigate the validity of the 4B-3C model for more highly charged ions. By comparing our calculations with experimental data and the three-distorted-wave eikonal-initial-state (3DW-EIS) approximation, we find the 4B-3C predict unique forward peak structures in the FDCS and broadly reproduce the experimental data over the entire angular range in a satisfactory manner for Au24+. Clear discrepancies are found between both theories and with experiment for Au53+.

Internuclear interaction on fully differential cross-sections for single ionization of helium by proton impact

The modified Coulomb-Born approximation including the proton impact internuclear interaction (MCB-PI) is applied to study single ionization of helium by 75 keV proton impact. Fully differential cross-sections (FDCS) are calculated both in the scattering and perpendicular planes. The results are compared with experimental data and theoretical predictions from the three-body distorted wave (3DW) and the continuum distorted wave-eikonal initial state (CDW-EIS). It is shown that the features of the FDCS are better reproduced by the MCB-PI results. We also assess the influence of the PI interaction on the FDCS and we find that the PI interaction is particularly important in the perpendicular plane.

Triply differential cross-sections for single ionization of sodium by electron impact in doubly symmetric geometry

Dynamically screened three-Coulomb-wave model (DS3C) is used to study the single ionization of the 3S orbital of sodium by electron impact. Triply differential cross-sections (TDCSs) are calculated in doubly symmetric geometry at excess energies of 6, 10, 15, 20, 30, 40, 50 and 60 eV using a parameterized optimized effective potential. Comparisons are made between recently experimental data and theoretical predictions of the three-Coulomb wave function (3C) approach and distorted-wave Born approximation (DWBA). The angular distribution of the present TDCS is found to qualitatively reproduce the reported experimental data. It is shown that dynamically screened effects are important in this geometry.

Identification of higher order contributions in three-dimensional (e,2e) cross-sections for helium

Fully differential cross-sections for single ionization of helium by 102 eV and by 1 keV electron impact have been obtained using an advanced reaction microscope. The data cover a large range of emission angles for a low-energy ( E ≤ 15 eV) electron and different scattering angles for the fast electron. Significant electron emission out of the projectile scattering plane in between the binary and the recoil lobes is observed. The experimental data are compared with theoretical predictions from a three-Coulomb wave function model.

Total and angular differential cross sections of electrons emitted in collision between antiprotons and helium atoms

We present total and angular differential single-ionization cross sections for antiproton–helium collisions in the energy range of 1–1000 keV within the framework of time-dependent coupled-channel-, a continuum distorted wave eikonal initial state and classical trajectory Monte Carlo methods. The results are compared with other theoretical results and experimental data.

Kinematically complete experiment on single ionization in 75-keVp+Hecollisions

We have measured and calculated fully differential single-ionization cross sections for the complete three-dimensional space in 75 keV p+He collisions. Several signatures of the projectile-residual-target-ion interaction, some of which are not observable for fast projectiles and for electron impact, are revealed. Some of these features are qualitatively reproduced by our calculations if this interaction is accounted for. However, overall the agreement between theory and experiment is not very good. Thus, our understanding of effects caused by the projectile-residual-target-ion interaction appears to be rather incomplete.

Projectile–Residual-Target-Ion Scattering after Single Ionization of Helium by Slow Proton Impact

0031-9007= We have measured fully differential single ionization cross sections for 75 keV p He collisions. At this relatively small projectile velocity, signatures of the projectile–residual-target-ion interaction, which are not observable for fast projectiles and for electron impact, are revealed rather sensitively. In fact, this interaction appears to be more important than the postcollision interaction, which so far was assumed to be the most important factor in higher-order effects for slow ion impact. These features are not well reproduced by our three-distorted-wave calculations.

Fully differential single ionization cross sections of helium by relativistic heavy-ion impact

We present three-dimensional images of fully differential cross sections for ionization of He by 1GeV/amu U92+ impact. This collision system corresponds to a relatively large perturbation (projectile charge to velocity ratio η=0.8) in spite of a relativistic projectile speed of 90% speed of light, representing a kinematic regime which so far is to a large extent still unexplored. Here, in spite of the large perturbation, higher-order contributions in the projectile–electron interaction are very small, but at the same time we find the projectile–residual target-ion interaction to be quite important.

Three-dimensional fully differential single ionization cross sections for 75 keV p + He collisions

We have studied fully differential cross sections (FDCS) for single ionization in 75 keV p + He collisions by measuring the recoil-ion momentum and the projectile momentum in coincidence. The measured FDCS are completely dominated by the binary peak while the recoil peak is absent. This is a clear signature of the post-collision interaction between the outgoing projectile and the ejected electron. Furthermore, our continuum distorted wave calculation demonstrates the importance of the projectile–target nucleus interaction. While the shape of the experimental FDCS is well reproduced by this calculation, there are significant discrepancies in magnitude.

Absolute doubly differential single-ionization cross sections in p+He collisions.

We have measured and calculated doubly differential single-ionization cross sections for 50{endash}150-keV {ital p}+He collisions as a function of the projectile energy loss and scattering angle. The measured cross sections were put on an absolute scale by normalizing the integrated cross sections to known total cross sections. Clear effects of the postcollision interaction (PCI) were observed in the scattered projectile spectra. Our singly differential cross sections as a function of projectile energy loss do not agree with corresponding cross sections obtained from electron spectroscopy. These discrepancies are attributed to the PCI. Our calculations including the PCI reproduce the shape of our data quite well; however, there are discrepancies in the absolute magnitude. {copyright} {ital 1996 The American Physical Society.}

Observation of postcollision effects in the scattered projectile spectra for ionizing proton-helium collisions.

We have measured and calculated doubly differential single ionization cross sections as a function of the scattering angle and the projectile energy loss for 50 to 150 keV proton-helium collisions. These cross sections show unexpected structures as a function of both the energy loss and the scattering angle, which are interpreted as due to the postcollision interaction. Although the effects of postcollision interactions have previously been observed in electron spectra, this is the first observation of such effects for the scattered protons.

Single- and double-ionization cross sections for angular scattering of fast protons by helium.

The angular scattering of ${\mathrm{H}}^{+}$ by He has been investigated for single ionization at energies of 0.5, 1.0, and 3.0 MeV; and for double ionization at 1.0 MeV. The classical-trajectory Monte Carlo method has been used within one- and two-electron models to illustrate the collision dynamics. The angular differential single-ionization cross sections are in good agreement with experiment, and display the combined effects of proton scattering from the He nucleus and its electrons. The relative fraction of double ionization, as a function of scattering angle, shows a maximum at \ensuremath{\sim}0.9 mrad that is in agreement with the experiments of Giese and Horsdal [Phys. Rev. Lett. 60, 2018 (1988)]. This maximum is found to be due to two uncorrelated scattering events between the ${\mathrm{H}}^{+}$ and the He atom's two electrons in the double-ionization reaction from impact parameters different than that for the single-ionization reaction.