Single and double electron capture cross sections in
keV-collisions between fully stripped ions with helium
atom

Aicha Ibaaz, Alain Dubois

► To cite this version:

Aicha Ibaaz, Alain Dubois. Single and double electron capture cross sections in keV-collisions between fully stripped ions with helium atom. Journal of Physics: Conference Series, 2015, 635 (2), pp.022044 10.1088/1742-6596/635/2/022044. [hal-01266426](https://hal.sorbonne-universite.fr/hal-01266426)

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Single and double electron capture cross sections in keV-collisions between fully stripped ions
with helium atom

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2015 J. Phys.: Conf. Ser. 635 022044

(http://iopscience.iop.org/1742-6596/635/2/022044)

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# Single and double electron capture cross sections in keV-collisions between fully stripped ions with helium atom

Aicha Ibaaz<fnref n="1" /> and Alain Dubois<fnref n="2" />

Laboratoire de Chimie Physique-Matière et Rayonnement,
Université Pierre et Marie Curie - CNRS, 75005 Paris, France

**Synopsis** We present cross section calculations for single-, double-capture, and double capture to auto-ionizing states occurring in the course of collisions between fully stripped ions Aq⁺ (q≤10) and helium atom at impact energies ranging from 0.25 to 625 keV/u. These calculations were performed by applying a semiclassical non-perturbative close coupling approach, based on the expansion of the scattering wave function into asymptotic bielectronic states with proper translational conditions and including both static and dynamic electronic correlation.

For the four last decades, the semiclassical nonperturbative close coupling formalism has been developed, improved and widely used to describe mainly mono-electronic processes occurring during collisions between atoms and molecules, neutral or charged. Such model has been proved to be reliable and unavoidable for intermediate impact energies, i.e. when the projectile-target relative velocity is of the same order of the (classical) velocity of the active electrons.

The objective of the present work is to apply this approach that has been recently improved to describe *ab initio* the dynamics of up to four electrons of the scattering system [1]. In the conference we shall report cross sections for collisions between He and fully stripped ions of elements of atomic number (Z<sub>p</sub>) up to 10 in the 0.25-625 keV/u impact energy domain. We shall especially focus on single capture (SC) and double electron capture (TDC) which are the important ones for the considered energies. The analysis of these processes shows that they strongly depend upon Z<sub>p</sub> and are highly final states selective. As an example, for Li<sup>3+</sup>-He collisions, SC mainly populates n=2 states and our results show good agreement with other theoretical [2] and experimental [3-4] data. Concerning TDC processes which are described for the first time by a true two-electron non perturbative approach we can distinguish true double capture (DC), for which the projectile keeps the two captured electrons, from DC into autonionizing states (AIDC), where the projectile loses one electron. We shall present detailed results concerning the relative contribution of these two processes as function of the projectile charge and impact velocity: for low Z<sub>p</sub> DC process is the dominant one while AIDC takes over for increasing Z<sub>p</sub>.

Our results for He<sup>2+</sup>-He and Li<sup>3+</sup>-He systems are in good agreement with the experimental data [3, 5] but that is not the case for the other systems for which rare results are available.

## References

[1] N. Sisourat, I. Pilskog and A. Dubois 2011 Phys. Rev. A **84** 052722

[2] L. F. Errea, F. Martin, L. Mendez, A. Riera and M. Yanez 1986 J. Chem. Phys. **84** 5422

[3] M. B. Shah and H. B. Gilbody 1985 J. Phys. B **18** 899

[4] J. A. Guffey, L. D. Ellsworth and J. R. MacDonald 1977 Phys. Rev. A **15** 5

[5] M. E. Rudd, T. V. Guffey and A. Itoh 1985 Phys. Rev. A **32** 4

<figure><img src="image_2.png" /></figure>

<footnote n="1">¹ E-mail: ibaaz.aicha@yahoo.com</footnote>

<footnote n="2">² E-mail: alain.dubois@upmc.fr</footnote>