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Montenegro, E. C.; Melo, Wilson S.; Meyerhof, W. E.; Pinho, A. G. de

doi:10.1103/physreva.48.4259

Cited by 24 publications

(21 citation statements)

References 36 publications

(35 reference statements)

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“…The target electron is the ionizing agent of the projectile and, due to the energy and momentum transfer to the projectile, has a high probability of being ionized simultaneously with the projectile electron. Thus, coincidence measurements for projectile and target final charge states can at least partially separate experimentally the screening and antiscreening processes specifying the cross sections σ p,q for the projectile (p) and target (q), final charge states [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…The He + + He and C 3+ + Ne are examples of collision systems for which the simultaneous screening ionization of both target and projectile masks the antiscreening contribution to projectile electron loss. For He + + He this is an important effect in the intermediate-to-low velocity range [9,10]. For C 3+ + Ne the effect is even stronger and the antiscreening contribution becomes negligible for low velocities [1].…”

Section: Introductionmentioning

confidence: 99%

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Dominant screening process in the projectile electron loss for F- + Ar collisions

Sant’Anna¹

2006

Braz. J. Phys.

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A comparison between projectile electron loss cross sections for negative, F − , and positive, He + , projectiles is presented for collisions with Ar target. The behavior of the two collision systems is similar for the projectile electron loss with target ionization. For projectile electron loss without target ionization (the so-called screening electron-loss process), quite different situations are presented for the studied positive and negative projectiles. For He + + Ar, the loss without target ionization collision channel is negligible for intermediate-to-low energies. On the other hand, for F − + Ar, this collision channel is the dominant one in the total projectile electron loss at intermediate-to-low velocities. The roles played by coupling with the electron capture by the projectile collision channel and by the very different binding energies for negative and positive projectiles are discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dominant screening process in the projectile electron loss for F- + Ar collisions

Sant’Anna¹

2006

Braz. J. Phys.

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“…Theory: solid line, total electron loss (sum of Eqs. In figure 1 the theoretical cross sections are compared with the experimental data for the electron loss of He + from DuBois [39], Montenegro et al [40], and Santos [38] as a function of the projectile energy. In the figure, the trian-gles, the diamonds, and the dashed line are the results for the single-loss -single-ionization process (case (ii), above), while the circles and the dotted line are those for the singleloss -double-ionization process (case (iii), above).…”

Section: Calculations Of the Probabilities And Cross Sectionsmentioning

confidence: 99%

“…Thus, a "cut-off" impact parameter of 3.5 au was chosen, because, for this value, the ionization probabilities for all the other mechanisms considered here are already negligible in the velocity range of the experimental data. [39], crosses [40], and solid squares [38], total electron loss; open triangles [39], open diamonds [40], and solid triangles [38], single-loss -single-ionization; open circles [39]) and solid circles [38], singleloss -double-ionization. Theory: solid line, total electron loss (sum of Eqs.…”

Section: Calculations Of the Probabilities And Cross Sectionsmentioning

confidence: 99%

“…In section 2, the main features of the IEVM are introduced and the recipes to obtain the total transition probabilities are fully presented. In section 3, the calculations are compared with the cross sections of total single-electron loss and electron loss accompanied by single and double ionization of the target of Li + and Li 2+ ions by He atoms [36,37], and of He + ions also by He atoms [38,39,40]. The specific contributions of the antiscreening mechanism to the total cross sections are analyzed in section 4.…”

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Two-center electron-electron correlation within the independent event model

Sigaud¹,

Montenegro²

2003

Braz. J. Phys.

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The Independent Event Model (IEVM) is used to analyze collision processes for systems with three and four electrons, in situations where up to three active electrons are involved and dynamical correlation effects play a major role. The model is applied to single electron loss and loss-ionization processes. All the possible ionization mechanisms for both collision partners in each exit channel are considered, including antiscreening, which, in the IEVM, can be taken into account in a consistent way along all the other ones, keeping unitarity. As a casestudy, the IEVM is applied to the analysis of the single loss of He + , Li + , and Li 2+ ions by He atoms with the simultaneous single and double ionization of the target. We present plots of the cross sections of single electron loss accompanied or not by the ionization of the target as functions of the projectile energy. The calculations describe well the experimental energy dependence and the high-velocity absolute values for the cross sections. I IntroductionCollisions between dressed ions -considered here as ions which carry electrons -and neutral atoms, when both collision partners have active electrons, present a multiplicity of possible simultaneous exit channels which result in singleor multi-electron transitions within and between the participating systems. Some of these channels include the single or multiple ionization of the projectile and of the target atom, followed -or not -by the capture of one -or more -target electrons by the incoming ion. Particular attention, from both the experimental and theoretical points of view, has been drawn in recent years to the simultaneous ionization of dressed projectiles colliding with neutral noble gas targets, which is governed by two competing mechanisms, the so-called direct loss-ionization and antiscreening modes [1,2,3,4]. The importance of the dynamical electron correlation in this type of collision is now well established, in particular at intermediate and high velocities, where the electron-electron interaction (antiscreening) can dominate the total electron loss cross section [5,6]. This has been evinced experimentally by the measurement either of total cross sections [7,8,9] or of the momentum distributions of the recoil ions, which provide a definite signature for the antiscreening mechanism [10,11,12,13].The simultaneous occurrence of competing processes, mainly when they include two-center electron correlation, renders difficult a comprehensive theoretical description of the collision. Only in the simplest cases, single-channel analyses can be used to describe properly the experimental results. The pioneering works of Bates and Griffing [14] provided the first description of such electron-loss processes within the first-Born approximation. Actually, the behavior of both the screening and the antiscreening modes for light targets is conveniently described by first-order models, such as the plane wave Born approximation (PWBA) [2,3,15,16,17].There are not many options available to treat collision syste...

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Two-center electron-electron interaction in projectile electron excitation and loss

Meyerhof

Montenegro

1994

Nuclear Instruments and Methods in Physics Research Section B:

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Intermediate-velocity atomic collisions. VI. Screening, antiscreening, and related processes inHe++(H2

Cited by 24 publications

References 36 publications

Dominant screening process in the projectile electron loss for F- + Ar collisions

Dominant screening process in the projectile electron loss for F- + Ar collisions

Two-center electron-electron correlation within the independent event model

Two-center electron-electron interaction in projectile electron excitation and loss

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