Introduction: Radiative transition parameters in Cs XI are essential for analyzing its extreme ultraviolet (EUV) spectrum and modeling high-temperature plasmas in various astrophysical and fusion environments. Cs XI, a Rh I isoelectronic sequence member, exhibits complex spectral features due to strong configuration interactions involving the ground configuration 4d9 and excited configurations such as 4d8nℓ, 4d7nℓ2, and 4p54d10. Previous studies have reported several energy levels and transition arrays, particularly 4d9 -4d85p and 4d9 - 4d84f; however, the strong mixing effects with the 4p54d10 configuration were not thoroughly considered. Consequently, a re-examination of Cs XI is necessary to improve the accuracy of transition probabilities and energy levels.
Methods: Comprehensive atomic structure calculations were performed using Cowan’s code suite, incorporating configuration interaction (CI) and valence–valence correlation effects. The LOPT code was used to optimize the known energy levels and to compute Ritz wavelengths with their uncertainties. Theoretical gA-values were determined and compared with previously reported data for consistency and validation.
Results and Discussion: The present analysis confirms all significant energy levels and transitions reported in earlier studies while providing refined gA-values that show improved agreement with observed spectra. The inclusion of configuration mixing with 4p54d10 substantially enhances the accuracy of transitions involving 4d84f levels. The calculated gA-values and associated uncertainties provide reliable data for plasma diagnostics and modeling of EUV spectra.
Conclusion: This study systematically re-evaluates Cs XI atomic parameters using extended HFR calculations. All known levels of Cs XI were optimized using the LOPT scheme, and thereby evaluated Ritz wavelengths were presented. The inclusion of the 4p54d10 configuration leads to enhanced accuracy and consistency in theoretical energy levels and gA-values. The refined dataset strengthens the reliability of Cs XI atomic data, which would be a valuable resource for spectroscopic studies and plasma modeling in laboratory and astrophysical applications.
