Comparison of Experimental and Theoretical Fully Differential Cross Sections for Single Ionization of the 2s and 2p States of Li By O⁸⁺ Ions

This paper presents a full three-dimensional (3D) comparison between experiment and theory for 24 MeV O8+ single ionization of the 2s ground state of lithium and the 2p excited state. Two theoretical approximations are examined: the three-body continuum distorted-wave (3DW) and three-body continuum distorted-wave-eikonal initial state (3DW-EIS). Normally, there is a significant difference between these two approaches and the 3DW-EIS is in much better agreement with experiment. In this case, there is very little difference between the two approaches and both are in very good agreement with experiment. For the excited 2p state, the 3D cross sections would exhibit a mirror symmetry about the scattering plane if all three magnetic sublevels were excited in equal proportions. For the present experiment, the 2p+1 (m=+1) sublevel is dominantly excited (quantization axis is the incident beam direction) and for this case there is a magnetic dichroism which is observed both experimentally and theoretically

A Self-Consistent Model for Positronium Formation from Helium Atoms

The differential and total cross sections for electron capture by positrons from helium atoms are calculated using a first-order distorted wave theory satisfying the Coulomb boundary conditions. In this formalism a parametric potential is used to describe the electron screening in a consistent and realistic manner. The present procedure is self consistent because (i) it satisfies the correct boundary conditions and post-prior symmetry, and (ii) the potential and the electron binding energies appearing in the transition amplitude are consistent with the wave functions describing the collision system. The results are compared with the other theories and with the available experimental measurements. At the considered range of collision energies, the results agree reasonably well with recent experiments and theories. [Note: This paper will be published on volume 42 of the Brazilian Journal of Physics

Two-effective-center approximation for proton-impact single ionization of hydrogen molecules

Some closed-form expressions are derived for the partial direct and indirect transition amplitudes for proton-impact single ionization of the hydrogen molecules using a first-order two-effective center continuum-wave approximation. The method satisfies the correct boundary conditions in the entrance channel. The basic assumption in this model is that when the active electron is ionized from one of the atomic centers in the molecule, the other scattering center is completely screened by the passive electron. Consequently, the transition amplitude can be expressed as a superposition of the partial ionization amplitudes from two independent scattering centers located at a constant distance from each other. The superposition of the partial amplitudes leads to different interference patterns for various orientations of the molecular target. The calculated cross sections are compared with the experiments and also with other theories. The comparison shows that the present results are reliable

Classical simulation of differential single charge transfer in fast proton-helium collisions

Three-body classical trajectory Monte Carlo method is employed to simulate the differential single electron capture process in fast proton-helium collisions. For the considered collisional system, by means of an independent particle model, both electron capture and electron excitation probabilities are evaluated in terms of the classical impact parameter and the related discussions are presented. The method is also applied to calculate the projectile-angular distribution of the cross sections in energy range of 50–630 keV. The obtained results are compared to the available precise data due to the cold-target recoil ion momentum spectroscopy and good overall agreement found with these experimental data. Also, within a classical-trajectory framework, the correlation between the impact parameter and the projectile scattering angle is examined through the simulation of the collision process

A four-body approach to electron-impact single ionization of helium atoms

A four-body approach based on the three-Coulomb distorted wave (3CDW) model is applied to study of the electron-impact single ionization of helium atoms. Triply differential cross sections (TDCS) are calculated for different values of the incident and ejection energies and various amounts of the scattering angles. The ejection angular distribution of the TDCS in general exhibits two peaks, binary and recoil peaks. The obtained results are compared with the available experimental data as well as other theoretical predictions. The comparison shows a good agreement between the present calculations and the measurements. Also, the obtained results are compatible with the other theories

Entanglement generation between two colliding particles

Entanglement generation in the one-dimensional collision of two initially uncorrelated spin-1/2 particles is analyzed. It is assumed that the colliding particles interact with each other through a delta potential with a spin-spin coupling strength. Two different approaches are followed. In the first approach, the colliding particles are described by plane waves and in the second one by Gaussian wave packets. It is shown that the collision process create a final state which may be entangled in both momentum and spin spaces. The magnitude of the created entanglement is a function of the potential strength, the initial spin state and the initial momentum of the particles. By changing the initial spin state of the system, an entanglement exchange occurs between the k and spin spaces. Also, the present wave-packet analysis demonstrates, somewhat surprisingly, that initial widths of the wave packets describing the colliding particles play but a minor role for the entanglement generation process

Large discrepancies observed in theoretical studies of ion-impact ionization of the atomic targets at large momentum transfer

A full quantum mechanical version of the three-body distorted wave-eikonal initial state (3DW-EIS) theory is developed to study of the single ionization of the atomic targets by ion impact at different momentum transfers. The calculations are performed both with and without including the internuclear interaction in the transition amplitude. For $16\ \text{Mev}\ \text{O}^{7+} \text{-He}~(1s^2 )$ and $24\ \text{Mev}\ \text{O}^{8+}\text{-Li}~(2s )$ collisions, the emission of the active electron into the scattering plane is considered and the fully differential cross-sections (FDCSs) are calculated for a fixed value of the ejected electron energy and a variety of momentum transfers. For both the specified collision systems, the obtained results are compared with the experimental data and with the cross-sections obtained using the semi-classical continuum distorted wave-eikonal initial state (CDW-EIS) approach. For $16\ \text{Mev}\ \text{O}^{7+} \text{-He}~(1s^2)$ , we also compared the results with those of a four-body three-Coulomb-wave (3CW) model. In general, we find some large discrepancies between the results obtained by different theories. These discrepancies are much more significant at larger momentum transfers. Also, for some ranges of the electron emission angles the results are much more sensitive to the internuclear interaction to be either turned on or off

Entanglement production in scattering of Gaussian wave packets from fixed localized impurities

Generation of quantum entanglement in scattering of particles from fixed localized spin impurities is investigated. In the suggested approach, the incident particle is described by a Gaussian wave packet with an initial definite width. It is also assumed that the incident particle interacts with the impurities through the Ising and/or Heisenberg interactions. It is shown that the created entanglement is strongly affected by the initial width of the incident wave packet. For an initially well localized wave packet the created entanglement is low. However, as the initial width increases the entanglement grows appreciably and for sufficiently large values of the initial width the present results tend to our previous results for scattering of plane waves from spin impurities. For scattering from a double spin impurity, it is shown that the periodic behavior of the previous results changes significantly