Formation of Kr${}^{3+}$ via core-valence doubly ionized intermediate states

Formation of Kr $^{3 +}$ via core-valence doubly ionized intermediate states

E. Andersson, P. Linusson, S. Fritzsche, L. Hedin, J. H. D. Eland, L. Karlsson, J.-E. Rubensson, and R. Feifel

Phys. Rev. A 85, 032502 – Published 5 March 2012

Abstract

The time-of-flight photoelectron-photoion coincidence technique has been used to study single-photon $3 d^{9} 4 p^{5}$ core-valence double ionization of Kr and subsequent Auger decay to triply charged states associated with the $4 s^{2} 4 p^{3}$ and $4 s^{1} 4 p^{4}$ configurations. The photon energy used was $h ν = 150$ eV. Multiconfiguration Dirac-Fock calculations were performed both for the doubly ionized intermediate states and the triply ionized final states. The intermediate states of Kr $^{2 +}$ are observed between 120 and 125 eV, whereas the final states of Kr $^{3 +}$ are observed between 74- and 120-eV ionization energy. Assignments of all structures are made based on the present numerical results. The calculated Auger rates give a detailed explanation of the relative line strengths observed.

Received 22 December 2011

DOI:https://doi.org/10.1103/PhysRevA.85.032502

Authors & Affiliations

E. Andersson¹, P. Linusson², S. Fritzsche^3,4,5, L. Hedin¹, J. H. D. Eland^1,6, L. Karlsson¹, J.-E. Rubensson¹, and R. Feifel¹

¹Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
²Department of Physics, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm, Sweden
³Department of Physics, P. O. Box 3000, Fin-90014 University of Oulu, Finland
⁴GSI Helmholtzzentrum für Schwerionenforschung D-64291 Darmstadt, Germany
⁵Frankfurt Institute for Advanced Studies, D-60438 Frankfurt am Main, Germany
⁶Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom

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Vol. 85, Iss. 3 — March 2012

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Images

Figure 1
Schematic energy level diagram of krypton in various charge states illustrating the processes studied in this work. Energy values given are based on data from Refs. [17, 29, 30, 31]. The energy levels of Kr $^{3 +}$ taken from NIST [31] have been corrected by 1.2 eV (see text for details).Reuse & Permissions
Figure 2
Triple electron coincidence map recorded at the photon energy $h ν = 150$ eV, which shows the formation of Kr $^{3 +}$ states by single Auger decay from Kr $^{2 +}$ $3 d^{9} 4 p^{5}$ intermediate states. The $y$ axis represents the kinetic energy sum of two electrons (a projection of it is shown in Fig. 3) which reflects the core-valence intermediate states. The $x$ axis represents the photon energy minus the total kinetic energy sum of all three electrons detected (the projection of it is shown in Fig. 4), and the $z$ axis represents coincidence counts per channel.Reuse & Permissions
Figure 3
Lower panel: Single photon core-valence double-ionization spectra of krypton recorded at $h ν = 150$ eV, obtained by integration along the $x$ axis of the data presented in Fig. 2. Upper panel: Simulated spectrum using the calculated Kr $^{2 +}$ $3 d^{9} 4 p^{5}$ state energies and photoionization amplitudes, convoluted with the expected experimental resolution and calculated lifetime widths. The calculated levels and relative intensities are indicated by bars, together with $L S$ term symbols.Reuse & Permissions
Figure 4
(a) Kr $^{3 +}$ electron spectrum formed by single Auger decay from Kr $^{2 +}$ $3 d^{9} 4 p^{5}$ intermediate states, obtained by integration along the $y$ axis of the data presented in Fig. 2. Energy levels from the NIST database [31] are indicated by bars. (b) A simulated spectrum based on calculated energy levels and Auger rates (see text), convoluted with the experimental resolution. Some of the calculated level energies have been replaced by experimental ones from the NIST database, as explained in the text, which is indicated in the spectrum. Auger rates have been weighted by intensities from Table corresponding to the intermediate state involved in the transition.Reuse & Permissions
Figure 5
Triple ionization spectra selected on the different core-valence intermediate state energy regions labeled $a$ – $e$ in Fig. 3. The triple ionization spectrum for decays from the entire spectral region of Fig. 3 is shown in the topmost panel in this figure. The intensities have been normalized with respect to the total intensity in the region between 70- and 110-eV ionization energy; the region above 110-eV energy has been excluded due to increased background noise.Reuse & Permissions
Figure 6
Simulated Auger-electron spectrum for transitions from Kr $^{2 +}$ $3 d^{9} 4 p^{5}$ states to Kr $^{3 +}$ , based on calculated Auger rates. The $L S$ terms for the individual intermediate states are given together with the label ( $a$ to $e$ ) of the corresponding experimental Kr $^{2 +}$ $3 d^{9} 4 p^{5}$ peak (cf. Fig. 3). At the top of the graph the label of the corresponding experimental peak is given (cf. Figs. 4 and 5).Reuse & Permissions

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