# Auger decay of the 4d 9 5s 2 5pnf excited states of Xe 5+ ion

J-M Bizau, D Cubaynes, S Guilbaud, M M Al Shorman, F Penent, P

Lablanquie, L Andric, J Palaudoux, C Blancard

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J-M Bizau, D Cubaynes, S Guilbaud, M M Al Shorman, F Penent, et al.. Auger decay of the 4d 9 5s 2 5pnf excited states of Xe 5+ ion. Journal of Physics: Conference Series, 2015, 635 (9), pp.092045 10.1088/1742-6596/635/9/092045. [hal-01265679](https://hal-fr.sorbonne-universite.fr/hal-01265679)

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Auger decay of the $4d^{9}5s^{2}5pnf$ excited states of $Xe^{5+}$ ion

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2015 J. Phys.: Conf. Ser. 635 092045

(http://iopscience.iop.org/1742-6596/635/9/092045)

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Auger decay of the 4d⁹⁵s²⁵pnf excited states of Xe⁵⁺ ion

J.-M. Bizau*§¹, D. Cubaynes*§, S. Guilbaud*, M.M. Al Shorman*, F. Penent†, P. Lablanquie†, L. Andric†, J. Palaudoux† and C. Blancard°

* ISMO, CNRS UMR 8214, Université Paris-Sud, Bât. 350, F-91405 Orsay cedex, France

§Synchrotron SOLEIL, L'Orme des Merisiers, St Aubin, BP48, F-91192 Gif-sur-Yvette, France

†LCPMR, CNRS & Univ. Paris 6, 11 rue Pierre et Marie Curie, F-75231 Paris Cedex 05, France

° CEA-DAM-DIF, Bruyère-le-Châtel, F-91297 Arpajon cedex, France

**Synopsis** The Auger decay of the 4d → nf (n = 4 to 6) photoexcitations in Xe⁵⁺ ion has been measured using electron spectrometry. MCDF calculations allow to interpret the recorded electron spectra.

Photoionization (PI) of free ionic species is a key process for plasmas modeling. Up to now, laboratory studies on multiply-charged ions were limited mainly to photoabsorption[1] and ionic spectrometry[2] experiments. Merged-beam setups in synchrotron radiation (SR) facilities provide absolute PI cross sections. Electron spectroscopy on ionic species is still a challenge due to the low target density. Its feasibility was demonstrated in the 90's on singly-charged atomic ions[3,4]. Since that time, only the high photon flux available at free electron lasers had allowed the observation of photoelectron spectra[5]. We present here the results of the first electron spectroscopy study performed on multiply-charged ions. The Auger spectra emitted in the decay of the 4d⁹⁵p5s²⁵nf resonances in Xe⁵⁺ ion, with n = 4 to 6, have been recorded.

The experiment was performed with the merged-beam setup of the PLEIADES beam line at SOLEIL French SR facility[6]. The Xe⁵⁺ ions were produced in an electron cyclotron resonance ion source (ECRIS). A cylindrical mirror electron analyzer (CMA), with its axis collinear to the ions and SR counter propagating beams, analyzed the kinetic energy of the electrons emitted in coincidence with the Xe⁶⁺ ions.

The Figure 1 shows an example of electron spectrum recorded at the photon energy of the 4d⁹⁵s²⁵p5f resonance (108.6 eV, upper panel). The Xe⁵⁺ ions are produced in the ECRIS in the 5p²P₁/₂ ground level and ²P₃/₂ metastable level. At this photon energy, resonances from both levels can be excited. At least four lines are observed and can be identified with the help of multi-configuration Dirac Fock (MCDF) calculations. The calculated electron spectrum (lower panel) is reconstructed assuming a 45% ²P₁/₂ and 55% ²P₃/₂ population and is convoluted with a Gaussian profile simulating the experimental broadening of the electron lines. All the lines

are issued from resonant PI processes of the type:

$$ \begin{aligned} & Xe^{5+} 5p^2 P_{1/2,3/2} + h\nu \rightarrow Xe^{5+} 4d^9 5s^2 5p5f \\ & Xe^{5+} 4d^9 5s^2 5p5f \rightarrow Xe^{6+} 5s^2 {}^1S + e^- \\ & Xe^{5+} 4d^9 5s^2 5p5f \rightarrow Xe^{6+} 5s5p {}^{1,3}P + e^- \end{aligned} $$

The good agreement between experimental and theoretical spectra shows that at this energy mainly Xe⁵⁺ ions in the ²P₃/₂ metastable level are excited, and that the main decay channel leads with equal intensity to the 5s² ¹S₀ ground level (main line at 44 eV kinetic energy) and to the 5s5p ³P₂ excited level of Xe⁶⁺ ion (satellite line observed at 30 eV).

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Electron spectrum recorded at 108.6 eV photon energy (top panel) compared to the reconstructed MCDF theoretical spectrum (bottom panel).</figcaption></figure>

References

[1] Kennedy E T *et al* 1994 *Opt. Eng.* **33** 3984–92

[2] Kjeldsen H 2006 *J. Phys. B At. Mol. Opt. Phys.* **39** R325–77

[3] Bizau J M *et al* 1991 *Phys. Rev. Lett.* **67** 576–9

[4] Gottwald A *et al* 1999 *Phys. Rev. Lett.* **82** 2068–70

[5] Domesle C *et al* 2013 *Phys. Rev. A* **88** 043405

[6] Gharaibeh M F *et al* 2011 *J. Phys. B At. Mol. Opt. Phys.* **44** 175208

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<footnote>§¹ E-mail: jean-marc.bizau@u-psud.fr</footnote>