Research Note

K-shell photoabsorption and photoionisation of trace elements

I. Isoelectronic sequences with electron number 3 ≤N ≤ 11

¹ Physique Atomique et Astrophysique, Université de Mons – UMONS, 20 place du Parc, 7000 Mons, Belgium
e-mail: patrick.palmeri@umons.ac.be
² IPNAS, Université de Liège, Campus du Sart Tilman, Bât. B15, 4000 Liège, Belgium
e-mail: pascal.quinet@umons.ac.be
³ Centro de Física, Instituto Venezolano de Investigación Científicas (IVIC), A.P. 21827, Caracas 1020, Venezuela
e-mail: claudio@ivic.gov.ve
⁴ Department of Physics, Western Michigan University, 1903 W Michigan Ave., Kalamazoo, MI 49008, USA
⁵ ADNET Systems, Inc., Bethesda, MD 20817, USA
⁶ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 8 March 2016
Accepted: 25 March 2016

Abstract

Context. With the recent launching of the Hitomi X-ray space observatory, K lines and edges of chemical elements with low cosmic abundances, namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn, can be resolved and used to determine important properties of supernova remnants, galaxy clusters and accreting black holes and neutron stars.

Aims. The second stage of the present ongoing project involves the computation of the accurate photoabsorption and photoionisation cross sections required to interpret the X-ray spectra of such trace elements.

Methods. Depending on target complexity and computer tractability, ground-state cross sections are computed either with the close-coupling Breit-Pauli R-matrix method or with the autostructure atomic structure code in the isolated-resonance approximation. The intermediate-coupling scheme is used whenever possible. In order to determine a realistic K-edge behaviour for each species, both radiative and Auger dampings are taken into account, the latter being included in the R-matrix formalism by means of an optical potential.

Results. Photoabsorption and total and partial photoionisation cross sections are reported for isoelectronic sequences with electron numbers 3 ≤ N ≤ 11. The Na sequence (N = 11) is used to estimate the contributions from configurations with a 2s hole (i.e. [2s]μ) and those containing 3d orbitals, which will be crucial when considering sequences with N > 11.

Conclusions. It is found that the [2s]μ configurations must be included in the target representations of species with N ≥ 11 as they contribute significantly to the monotonic background of the cross section between the L and K edges. Configurations with 3d orbitals are important in rendering an accurate L edge, but they can be practically neglected in the K-edge region.