Simultaneous excitation-ionization of helium at five times threshold

Rouvellou, B.; Rioual, Stéphane; Pochat, A.; Tweed, R J; Langlois, J.; Vien, G. Nguyen; Robaux, O.

doi:10.1088/0953-4075/33/17/101

Cited by 21 publications

(28 citation statements)

References 19 publications

(30 reference statements)

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“…Even for the coplanar geometry, significant discrepancies between theory and experiment can occur under such conditions, if the part of the projectile-target interaction responsible for ionization is accounted for only to first order [12]. Such experiments were performed by Dupré et al [13] and later by Avaldi et al [14] and Rouvellou et al [15]. For their conditions of highly asymmetric energy sharing between the two outgoing electrons, hybrid methods based upon a perturbative treatment, up to second order, of the projectile-target interaction and an R matrix (closecoupling) approach for the ejected-electron-residual-ion interaction [16] were quite successful, especially when the latter part of the problem (e-He collisions) was systematically driven to convergence [17].…”

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confidence: 99%

Electron-Impact Ionization and Excitation of Helium to then=1–4Ionic States

2006

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We present high-precision (e,2e) measurements and calculations for the e-He four-body Coulomb breakup problem. Cross-section ratios for ionization and excitation of the first three excited states of He+ relative to the ground state have been measured for incident energies between 112 and 319 eV. Comparing the data with predictions from a state-of-the-art hybrid distorted-wave+convergent R matrix with pseudostates (close coupling) approach shows that treating the projectile-target interaction at least to second order is crucial to obtain reasonable agreement between theory and experiment. Nevertheless, our benchmark studies reveal significant theoretical problems for the symmetric energy-sharing cases, thus indicating the need for further improvement.

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confidence: 99%

Electron-Impact Ionization and Excitation of Helium to then=1–4Ionic States

2006

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“…In a recent paper Rouvellou et al (2000) reported new measurements of (e, 2e) excitationionization of ground state helium to He + (n = 2) at an impact energy of 365.8 eV. These measurements were made in coplanar asymmetric geometry and their purpose was to extend to lower energies the available data in this geometry (Stefani et al 1990, Dupré et al 1992, Avaldi et al 1998.…”

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Excitation-ionization of helium to He⁺(n= 2) at 365.8 eV

Marchalant

Rouvellou

Rasch

et al. 2000

J. Phys. B: At. Mol. Opt. Phys.

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“…However, the comparison between these predictions and the experimental data obtained by Stefani et al [9], Bellm et al [10,11], Dürr et al [12], Rouvellou et al [13], and Dogan and Crowe [14] shows that the agreement is far from being perfect. On the one hand, higher-order contributions could be significant.…”

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confidence: 82%

Electron-impact ionization excitation of helium in the quasiphoton regime

et al. 2010

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The triply differential cross section of ionization excitation of helium, leaving the residual ion in the n = 2 excited states, is evaluated for the kinematics considered experimentally by Dupré et al. [J. Phys. B 25, 259 (1992)]. The interaction of the incident electron with the target is described at the first order, while the interaction of the ejected electron with the residual ion is treated very accurately within the formalism of the Jacobi matrix method. In the quasiphoton limit and for low ejected electron energies, the presence of series of doubly excited states, mainly below the n = 3 single ionization threshold in helium, makes the triply differential cross sections extremely sensitive to both the energy and the emission angle of the ejected electron. We show that the convolution of our results with a Gaussian energy profile, in which the full width at half-maximum corresponds to the energy resolution in the experiment, has a significant effect. Our results suggest that it is also important to account for the finite resolution on the measurement of the scattering angle when the experimental data are compared to the theoretical predictions. Comparison of our theoretical results convoluted both in energy and in angle with the experimental data demonstrates the importance of an accurate description of the helium spectrum. A possible two-step mechanism involving single ionization of the target followed by excitation of the core electron is proposed to explain the remaining discrepancies.

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Simultaneous excitation-ionization of helium at five times threshold

Cited by 21 publications

References 19 publications

Electron-Impact Ionization and Excitation of Helium to then=1–4Ionic States

Electron-Impact Ionization and Excitation of Helium to then=1–4Ionic States

Excitation-ionization of helium to He⁺(n= 2) at 365.8 eV

Electron-impact ionization excitation of helium in the quasiphoton regime

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Simultaneous excitation-ionization of helium at five times threshold

Cited by 21 publications

References 19 publications

Electron-Impact Ionization and Excitation of Helium to then=1–4Ionic States

Electron-Impact Ionization and Excitation of Helium to then=1–4Ionic States

Excitation-ionization of helium to He+(n= 2) at 365.8 eV

Electron-impact ionization excitation of helium in the quasiphoton regime

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Excitation-ionization of helium to He⁺(n= 2) at 365.8 eV