Dielectronic and Radiative Recombination of Pm-like Tungsten (W XIV): A Relativistic Benchmark for Kilonova Modelling

In Non-Local Thermodynamic Equilibrium (Non-LTE) plasmas, the ionization balance and excited-state populations are heavily determined by radiative (RR) and dielectronic (DR) recombination [1]. Accurate data for these processes are thus fundamental to the interpretation of spectral signatures. For kilonova-relevant ions, however, experimental data remains insufficient for spectral modelling, and therefore requires RR and DR data to be theoretically calculated [1,2].

To establish a reliable methodology, first, we perform a benchmark calculation on Pm-like tungsten (W XIV). Tungsten is extensively studied throughout its ionization sequence, providing a wealth of available data for comparison [3,4]. This particular charge state mimics the complicated open f-shell structure of key r-process elements and, consequently, the challenges that arise while performing this type of calculation [5].

In this work, we present primarily RR and DR rate coefficients for W XIV while including other relevant quantities: RR and photoionization cross-sections and precise DR resonance energies. All calculations were made using the well-established Flexible Atomic Code (FAC) [6], which handles the intricate ion structure at a relatively low computational cost. These results provide high confidence in our method, enabling us to subsequently address the lanthanide sequence.

[1] Singh, S. et al., A&A., 700, A110. 2025

[2] Pognan, Q. et al., MNRAS, 510, 3806. 2022

[3] Trzhaskovskaya, M.B. et al., At. Data Nucl. Data Tables, 139, 101389. 2021

[4] Trzhaskovskaya, M.B. et al., At. Data Nucl. Data Tables, 94, 71. 2008

[5] Preval, S. P. et al., J. Phys. B, 52, 025201. 2019

[6] M.F. Gu, Can. J. Phys., 86, 675. 2008