Threshold Law For Positron Impact Ionization of Atoms

Ihra, W.; Macek, J. H.; Mota-Furtado, F.; O’Mahony, Patrick

doi:10.1103/physrevlett.78.4027

Cited by 42 publications

(25 citation statements)

References 18 publications

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“…For the positronimpact ionization the applicability domain is even less [12] [13]. As argued by Ihra et al [18], an agreement with experimental data could be substantially improved if the interaction of different modes in the deviation from SC is taken into account. Possibly some procedure to assess for the mode interaction could be developed also for the multifragment system;…”

Section: F Fragmentation In Two Pairs Of Identical Particles With Opmentioning

confidence: 99%

Threshold laws for the breakup of atomic particles into several charged fragments

Kuchiev

Ostrovsky

1998

Phys. Rev. A

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The processes with three or more charged particles in the final state exhibit particular threshold behavior, as inferred by the famous Wannier law for (2e + ion) system. We formulate a general solution which determines the threshold behavior of the cross section for multiple fragmentation. Applications to several systems of particular importance with three, four and five leptons (electrons and positrons) in the field of charged core; and two pairs of identical particles with opposite charges are presented. New threshold exponents for these systems are predicted, while some previously suggested threshold laws are revised.

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Section: F Fragmentation In Two Pairs Of Identical Particles With Opmentioning

confidence: 99%

Threshold laws for the breakup of atomic particles into several charged fragments

Kuchiev

Ostrovsky

1998

Phys. Rev. A

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“…As a result, the cross section becomes path dependent. The correction term can be included in a consistent way by following the prescription for the paths given in [6]; we refer to these calculations as HHCM +cor .The HHCM has previously been applied with success to three-body collisions, including electron excitation [1] and impact ionization [1,[7][8][9][10][11][12]. Earlier HHCM calculations for Ps(1s) formation in e + − H collisions included an asymptotic approximation to the correction term (for the P-and D-waves) and provided an explanation for the small S-wave Ps(1s)-formation cross section in terms of the Stückelberg phase [2].…”

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confidence: 99%

Hyperspherical hidden crossing method applied to Ps(1s)-formation in low energy e⁺− H, e⁺− Li and e⁺− Na collisions

Ward

Shertzer

2012

New J. Phys.

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The hyperspherical hidden crossing method with the correction term (HHCM +cor ) has been used to calculate partial wave Ps(1s)-formation cross sections for low-energy e + − H, e + − Li and e + − Na collisions. The Stückelberg phase varies in a systematic way as a function of atomic number Z , incident positron momentum k + , and total orbital angular momentum L and provides an explanation for the small S-wave cross section for all three systems. 13 References 13 Including the correction term does not compromise the simplicity of the method; it simply provides an improved value for the wave vector K (R). However, there is one undesirable consequence of using the correction term. The correction term diverges at the branch point, and therefore we include it only on the real axis. As a result, the cross section becomes path dependent. The correction term can be included in a consistent way by following the prescription for the paths given in [6]; we refer to these calculations as HHCM +cor .The HHCM has previously been applied with success to three-body collisions, including electron excitation [1] and impact ionization [1,[7][8][9][10][11][12]. Earlier HHCM calculations for Ps(1s) formation in e + − H collisions included an asymptotic approximation to the correction term (for the P-and D-waves) and provided an explanation for the small S-wave Ps(1s)-formation cross section in terms of the Stückelberg phase [2]. The HHCM was also used to treat near-threshold positron impact ionization of hydrogen [13]. The HHCM enables one to understand why the S-wave cross section for any process for e + − H collisions (including ionization) that proceeds via the Ps(1s) formation channel is small. Although the HHCM was derived for three-body Coulomb systems, it has been successfully used to study the recombination of three identical bosons with zero range two-body potentials [14]. We previously used the HHCM to calculate partial wave Ps(1s)-formation cross sections for e + − Li collisions [15]. Despite the success of these calculations, the application of the HHCM has been somewhat limited.We have carried out a systematic study of Ps(1s) formation in positron collisions with H, Li and Na using the HHCM +cor . The HHCM +cor results for e + − H and e + − Na reported here are new; we also include the previously published HHCM +cor e + − Li results [6] for completeness. We examine the behavior of the Stückelberg phase as a function of atomic number Z , incident positron momentum k + , and total orbital angular momentum L for the three atoms with a single l = 0 valence electron. For the alkalis, we use a model potential to describe the interaction of the valence electron and the positron with the ion core.

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“…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.…”

mentioning

confidence: 99%

“…This is particularly reflected by the decisively different threshold laws for total breakup (cf. [3][4][5] and references therein).…”

mentioning

confidence: 99%

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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Threshold Law For Positron Impact Ionization of Atoms

Cited by 42 publications

References 18 publications

Threshold laws for the breakup of atomic particles into several charged fragments

Threshold laws for the breakup of atomic particles into several charged fragments

Hyperspherical hidden crossing method applied to Ps(1s)-formation in low energy e⁺− H, e⁺− Li and e⁺− Na collisions

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

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Threshold Law For Positron Impact Ionization of Atoms

Cited by 42 publications

References 18 publications

Threshold laws for the breakup of atomic particles into several charged fragments

Threshold laws for the breakup of atomic particles into several charged fragments

Hyperspherical hidden crossing method applied to Ps(1s)-formation in low energy e+− H, e+− Li and e+− Na collisions

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

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Hyperspherical hidden crossing method applied to Ps(1s)-formation in low energy e⁺− H, e⁺− Li and e⁺− Na collisions