Dielectronic recombination rate coefficients of Rh-like In 4+ and W 29+ ions

Abstract We calculate Maxwellian-averaged DR rate coefficients for rhodium-like \(\mathrm{In}^{4+}\) and \(\mathrm{W}^{29+}\), representing medium- and high-\(Z\) ions, respectively, using the fully relativistic Dirac-Fock-Slater method implemented in the Flexible Atomic Code (FAC). The calculated results show distinct low-temperature DR behaviors for the two ions. For \(\mathrm{In}^{4+}\), the low-temperature resonance is mainly associated with inter-shell \((\Delta n=1)\) excitation channels, whereas for \(\mathrm{W}^{29+}\), intra-shell \((\Delta n=0)\) channels, especially those related to $4p$-$4f$ excitations, make a much larger contribution to the low-temperature DR peak. Convergence tests are also performed to assess the stability of the calculated DR rate coefficients with respect to the inclusion of higher Rydberg states. This difference suggests that increasing nuclear charge modifies the competition among excitation channels in high-\(Z\) rhodium-like ions, with relativistic atomic-structure effects providing an important contribution to this trend. Compared with published data, the present results show noticeable deviations in the low-temperature region, which are associated with differences in configuration selection, threshold positions, and the treatment of near-threshold resonance structures, to which the low-temperature DR rate is found to be highly sensitive, while the high-temperature trends remain consistent. Fitted DR parameters are further provided for the total rate coefficients and the main contributing channels, facilitating their use in plasma modeling and related spectroscopic applications.