Auger decay of the $3d$ hole in the isoelectronic series of Br, ${\mathrm{Kr}}^{+}$, and ${\mathrm{Rb}}^{2+}$

Auger decay of the $3 d$ hole in the isoelectronic series of Br, ${Kr}^{+}$ , and ${Rb}^{2 +}$

J. Keskinen, K. Jänkälä, S.-M. Huttula, T. Kaneyasu, Y. Hikosaka, E. Shigemasa, H. Iwayama, K. Soejima, K. Ito, L. Andric, M. A. Khalal, J. Palaudoux, F. Penent, and P. Lablanquie

Phys. Rev. A 103, 032828 – Published 22 March 2021

Abstract

The Auger decay process of the $3 d_{5 / 2}$ hole is studied experimentally and theoretically along the isoelectronic Br, ${Kr}^{+}$ , and ${Rb}^{2 +}$ series with electron configuration [Ar] $3 d^{9} 4 s^{2} 4 p^{6}$ . The experimental results consist of multielectron coincidence data measured from all three elements and conventional high-resolution Auger spectrum for the Br case. Theoretical interpretation was done by using multiconfiguration Dirac-Fock calculations. It is found that the decay rate of two-Auger-electron emission increases along the series in the direction of decreasing nuclear charge. Also, complexity of the Auger spectrum follows the same trend, requiring a drastic increase to the size of the configuration space for describing the observed spectra.

Received 30 September 2020
Accepted 11 February 2021

DOI:https://doi.org/10.1103/PhysRevA.103.032828

Physics Subject Headings (PhySH)

Autoionization & Auger processes Electronic structure of atoms & molecules Electronic transitions

Atoms

Photoionization

Atomic, Molecular & Optical

Authors & Affiliations

J. Keskinen ^1,*, K. Jänkälä ¹, S.-M. Huttula¹, T. Kaneyasu ², Y. Hikosaka³, E. Shigemasa⁴, H. Iwayama⁴, K. Soejima⁵, K. Ito⁶, L. Andric⁷, M. A. Khalal⁷, J. Palaudoux⁷, F. Penent⁷, and P. Lablanquie⁷

¹Nano and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland
²SAGA Light Source, Tosu 841-0005, Japan
³Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
⁴Institute for Molecular Science, Okazaki 444-8585, Japan
⁵Department of Environmental Science, Niigata University, Niigata 950-2181, Japan
⁶Société Civile Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, Boîte Postale 48, 91192 Gif-sur-Yvette Cedex, France
⁷Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 4 Place Jussieu, 75005 Paris, France

^*juho.keskinen@oulu.fi

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Vol. 103, Iss. 3 — March 2021

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Figure 1
(a) The electron spectrum measured on the HBr ( $3 d_{5 / 2} \to σ^{*}$ ) resonance at a photon energy of $h ν = 70.7$ eV (solid black line). It contains atomic lines due to the Auger decay of the Br atom formed upon ultrafast dissociation [22] and molecular lines due to photoionization processes in the HBr molecule. This last contribution is estimated off-resonance at 75.3 eV (dotted red line). Its subtraction gives in panel (b) the estimated Auger spectrum associated with the decay of the Br $3 d_{5 / 2}^{- 1} 4 s^{2} 4 p^{6}$ state. Panel (c) represents the electron-electron energy correlation map measured on the ( $3 d_{5 / 2} \to σ^{*}$ ) resonance in HBr. The recorded coincidence counts are coded by colors. Panel (e) shows the double-photoionization spectrum (solid black line) measured on the HBr ( $3 d_{5 / 2} \to σ^{*}$ ) resonance, extracted by integrating diagonally the coincidence map (c), as well as the off-resonance spectrum (dotted red line). Subtraction of this molecular component gives in panel (d) the ${Br}^{2 +}$ dicationic states populated by double-Auger decay of the $3 d_{5 / 2}^{- 1} 4 s^{2} 4 p^{6}$ state as a solid black line (the dashed part is a guide to the eye to highlight the atomic lines; the broad band above 32 eV appearing in panel (e) is due to the weaker molecular decays of the HBr ( $3 d \to σ^{*}$ ) resonance). Each label denotes the main contributing configuration of the corresponding line group. The spectra are presented as a function of the kinetic energy of the electrons (bottom axis) or as a function of binding energy of the ${Br}^{+}$ and ${Br}^{2 +}$ states (top axis) referenced to the Br $4 s^{2} 4 p^{5}$ ( ${}^{2}P_{3 / 2}$ ) ground-state level.
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Figure 2
Measured (b, c) and simulated (d) Auger spectra resulting from the decay of the Br $3 d_{5 / 2}^{- 1} 4 s^{2} 4 p^{6}$ state. The high-resolution Auger spectrum in panel (b) has been obtained with the procedure explained for Fig. 1 by subtracting an off-resonance spectrum [dotted red line in panel (a)] from the spectrum measured on the HBr ( $3 d_{5 / 2} \to σ^{*}$ ) resonance [solid black line in panel (a)]. Panel (c) is the low-energy resolution Auger spectrum of Fig. 1. The dashed lines act as guides to the eye. The dotted line in panel (d) represents simulated spectra (fac) without accounting for the line broadening due to the subsequent decay. Vertical lines with hatched areas indicate the upper kinetic energy limit for the double-Auger path. Labels correspond to the different contributing configurations in the following manner: a: $4 s^{0} 4 p^{6}$ , $b_{1}$ : $4 s 4 p^{4} (5 s, 6 / 7 / 9 d)$ , $b_{2}$ : $4 s 4 p^{4} 4 d$ , $c_{1}$ : $4 s^{2} 4 p^{3} 4 d$ , $c_{2 x}$ : $4 s^{2} 4 p^{3} (5 s, n d)$ , d: $4 s 4 p^{5}$ , and e: $4 s^{2} 4 p^{4}$ . Bracketed labels correspond to configurations that strongly mix with the main contributing configurations. In the case of $c_{2 x}$ additional $n / n ℓ$ labeling marked above the corresponding peaks defines the configuration in more detail.
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Figure 3
Measured and simulated Auger spectra resulting from the decay of the $3 d_{5 / 2}$ hole of the isoelectronic $3 d^{9} 4 s^{2} 4 p^{6}$ states in the Br, ${Kr}^{+}$ , and ${Rb}^{2 +}$ series. In each emboldened frame the upper panel (blue) depicts the experimental spectrum whereas the lower one (red) shows the results of the theoretical simulation (fac) with the contribution of the subsequent Auger decay to the width added. Experimental intensities are the measured count numbers divided by 1000. Vertical lines with hatched areas in the Br and ${Kr}^{+}$ experimental spectra indicate the upper kinetic energy for the double-Auger path. Labels to assign the dominant configurations in the simulations are explained in the legend of Fig. 2.
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Figure 4
Energy diagram showing states of interest in the Br, ${Kr}^{+}$ , and ${Rb}^{2 +}$ series. For all species, the column on the left reports the energy levels of the $3 d^{- 1} 4 s^{2} 4 p^{6}$ states, the middle one shows selected atomic states populated in single-Auger decay, and the one on the right gives states formed in double-Auger decay. All levels are referenced relative to the $3 d^{10} 4 s^{2} 4 p^{5}$ ( ${}^{2}P_{3 / 2}$ ) ground state. The $3 d^{- 1}$ levels are obtained for Br from Ref. [19], for ${Kr}^{+}$ from Ref. [33], and for ${Rb}^{2 +}$ from the Ph.D. thesis of Khalal [18]. The other levels are from the NIST tables [34].
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Figure 5
Energy sharing between the two Auger electrons emitted in the double-Auger decay of the Br $3 d_{5 / 2}$ hole and populating respectively the ${Br}^{2 +} 4 s^{2} 4 p^{3}$ ( ${}^{2}D$ ), $4 s^{2} 4 p^{3}$ ( ${}^{4}S$ ), or $4 s 4 p^{4}$ ( ${}^{2}D$ ) final states. The spectra are obtained from the intensities along the diagonal lines in Fig. 2 and the bin step for the three data curves is 10 meV.
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Figure 6
Comparison of the measured Auger spectrum resulting from the decay of the ${Rb}^{2 +} 3 d_{5 / 2}^{- 1}$ state with the spectrum simulated using grasp2k (brown) and fac (red) presented in kinetic energy. Experimental intensities are the measured count numbers divided by 1000. Labels to assign the dominant configurations in the simulations are explained in the legend of Fig. 2.
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Physical Review A

covering atomic, molecular, and optical physics and quantum information

Auger decay of the $3 d$ hole in the isoelectronic series of Br, ${Kr}^{+}$ , and ${Rb}^{2 +}$

J. Keskinen, K. Jänkälä, S.-M. Huttula, T. Kaneyasu, Y. Hikosaka, E. Shigemasa, H. Iwayama, K. Soejima, K. Ito, L. Andric, M. A. Khalal, J. Palaudoux, F. Penent, and P. Lablanquie

Phys. Rev. A 103, 032828 – Published 22 March 2021

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Physical Review A

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Auger decay of the 3d hole in the isoelectronic series of Br, Kr+, and Rb2+

J. Keskinen, K. Jänkälä, S.-M. Huttula, T. Kaneyasu, Y. Hikosaka, E. Shigemasa, H. Iwayama, K. Soejima, K. Ito, L. Andric, M. A. Khalal, J. Palaudoux, F. Penent, and P. Lablanquie

Phys. Rev. A 103, 032828 – Published 22 March 2021

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Auger decay of the $3 d$ hole in the isoelectronic series of Br, ${Kr}^{+}$ , and ${Rb}^{2 +}$