Evidence for Two-Centre Effects in the Electron Emission from 25 MeV/u Mo
                    <sup>40+</sup>
                    + He Collisions: Theory and Experiment

Stolterfoht, N.; Schneider, D.; Tanis, J. A.; Altevogt, H.; Salin, A.; Fainstein, P D; Rivarola, R D; Grandin, J. P.; Scheurer, J. N.; Andriamonje, S.; Bertault, D.; Chemin, J. F.

doi:10.1209/0295-5075/4/8/007

Cited by 107 publications

(30 citation statements)

References 22 publications

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“…p b 2 e, where e ø 1. This behavior has also been encountered in ionatom ionizing collisions (both experimentally and theoretically) [16,23,28,29,[32][33][34][35] and has been dubbed cusp asymmetry. To my knowledge there is as yet no clear physical explanation of the origin of this asymmetry and, as will be shown below, this study sheds new light on this question but certainly does not resolve it.…”

Section: Fig 2 the Same As Inmentioning

confidence: 79%

“…On the other hand, the phenomenon of electron capture to the projectile's continuum (ECC) is well established in heavy ion-atom ionizing collisions both experimentally and theoretically [17][18][19][20][21][22][23][24][25][26][27][28]. From these studies it has been concluded that a theoretical description of the energy and angular distributions of the secondary electrons must account for the interaction of these electrons both with the residual ion and the projectile [29]. For light-particle impact, such as positron, the theoretical description is even more challenging, for in this case the projectile is deflected through very large angles [11,15].…”

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confidence: 99%

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Asymmetric Formation of Positronium Continuum States Following Positron-Impact Ionization ofH2

Berakdar

1998

Phys. Rev. Lett.

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The fully differential cross section for the positron-and electron-impact ionization of H 2 is calculated. For positron impact the results are contrasted against a recent experiment which evidently shows the influence of the electron capture to a low-lying positronium continuum state. From a detailed analysis it is deduced that the capture probability is dependent on the orientation of the electron-positron relative momentum vector with respect to the residual ion. Within the used model, this asymmetric positronium formation is traced back to the distortion of the positron motion by the two-center potential formed by the residual ion and the secondary electron. [S0031-9007(98)06857-4] A detailed understanding of correlated many-body scattering states is of fundamental importance for diverse fields of physics such as discharge and plasma physics, fusion physics, and physics of the upper atmosphere. Such continuum states are usually achieved as the final outcome of charged particle-and photon-impact ionization. Recent technological advances in multiple detection techniques have rendered possible an unprecedented insight into the properties of these states: the energy and momentum transfer to the many-body continuum can be probed independently by virtue of equivelocity heavy-and lightparticle impact; for a fixed amount of energy and momentum transferred to the final state, the open reaction channels as well as the total potential surface can be varied using particle and antiparticle projectiles.A unified description of all of these facets is a major challenge for current theoretical investigations.The present study is motivated by a recent kinematically complete experiment [1] in which a H 2 molecule is ionized upon positron impact. The resulting final continuum states which consist of a positron and an electron moving in the field of H 1 2 [hereafter referred to as ͑e 2 e 1 H 1 2 ͒] have been simultaneously resolved in angle and energy.Contrasting this final channel with that achieved in electron-impact ionization [two electrons in the double continuum of a residual ion, labeled hereafter by ͑e 2 e 2 H 1 2 ͒], two distinctive differences can be noted. (i) Evidently the total potential surface is markedly different in both cases [2] which results in completely different dynamics. This is particularly reflected by the decisively different threshold laws for total breakup (cf. [3][4][5] and references therein).(ii) The indistinguishability of the two electrons introduces exchange effects in the case of ͑e 2 e 2 H 1 2 ͒, i.e., the cross sections are statistical mixtures of triplet and singlet scattering cross sections. While this effect is absent in the case of ͑e 2 e 1 H 1 2 ͒, an additional channel opens, namely, that of positronium formation.In the experiment of Kövér and Laricchia [1], capture of the ejected electron to low-lying positronium contin-uum states can be identified. This channel shows up as a rapid increase in the cross section when the electron approaches the positron in velocity space. The function...

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Section: Fig 2 the Same As Inmentioning

confidence: 79%

mentioning

confidence: 99%

Asymmetric Formation of Positronium Continuum States Following Positron-Impact Ionization ofH2

Berakdar

1998

Phys. Rev. Lett.

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“…represents a plane wave in the projectile reference frame, and D+(Z, q~r) = D (Z, q~r)' = N(v) iF, (iv;1;iqr + iq r) (1&) [14].…”

Section: A the Initial Channelmentioning

confidence: 99%

Binary-encounter electron production in energetic heavy-bare-ion–atom collisions

1992

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The production of binary-encounter electrons in heavy-ionatom collisions at high impact velocities is studied. The theoretical model used is the continuum-distorted-waveeikonal-initial-state approximation. Deviations from classical predictions for the height and position of the associated peak in double-differential cross sections are determined. A simple adiabatic resonant-tunneling model is developed to interpret the physical meaning of the shift in the position of the binary-encounter peak.PACS number(s): 34.50.Fa, 34.70.+e

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“…The importance of such two-center effects has recently been recognized. 12 " 14 The He target was described by the independentelectron model, 15 with an effective charge of 1.6875 and the experimental binding energy of 24.58 eV. It should be noted that the CTMC method directly includes the angular scattering of the projectile, the recoil of the target nucleus (which we have found to be important in the angular scattering of light projectiles), and the effects of electron capture (for positively charged projectiles).…”

Section: Dynamics Of Antimatter-atom Collisionsmentioning

confidence: 99%

Dynamics of Antimatter-Atom Collisions

Olson

Gay

1988

Phys. Rev. Lett.

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Evidence for Two-Centre Effects in the Electron Emission from 25 MeV/u Mo ⁴⁰⁺ + He Collisions: Theory and Experiment

Cited by 107 publications

References 22 publications

Asymmetric Formation of Positronium Continuum States Following Positron-Impact Ionization ofH2

Asymmetric Formation of Positronium Continuum States Following Positron-Impact Ionization ofH2

Binary-encounter electron production in energetic heavy-bare-ion–atom collisions

Dynamics of Antimatter-Atom Collisions

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Evidence for Two-Centre Effects in the Electron Emission from 25 MeV/u Mo 40+ + He Collisions: Theory and Experiment

Cited by 107 publications

References 22 publications

Asymmetric Formation of Positronium Continuum States Following Positron-Impact Ionization ofH2

Asymmetric Formation of Positronium Continuum States Following Positron-Impact Ionization ofH2

Binary-encounter electron production in energetic heavy-bare-ion–atom collisions

Dynamics of Antimatter-Atom Collisions

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Product

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Evidence for Two-Centre Effects in the Electron Emission from 25 MeV/u Mo ⁴⁰⁺ + He Collisions: Theory and Experiment