Calculated radiative transition probabilities and oscillator strengths are reported for 392 lines of neutral lanthanum (La I) atom in the spectral range from the near ultraviolet to the mid infrared. They were obtained using two different theoretical methods based on the pseudo-relativistic Hartree–Fock (HFR) and the fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) approaches, both including the most important intravalence and core-valence electron correlations. The quality of these radiative parameters was assessed through detailed comparisons between the results obtained using different physical models and between our theoretical results and the experimental data, where available. Of the total number of La I lines listed in the present work, about 60% have gf- and gA-values determined for the first time.

We report a comprehensive list of accurate Ritz wavelengths and calculated transition probabilities for parity-forbidden [Mn ii] lines. Ritz wavelengths have been derived from experimentally established energy level values resulting from an extensive analysis of a high-resolution Fourier-transform emission spectrum of singly ionized manganese. Our analysis includes transitions between all known metastable and other long-lived levels of Mn ii giving a total of 1130 [Mn ii] Ritz wavelengths. Our entire list of derived Ritz wavelengths for [Mn ii] lines ranges between 237 nm and 170 μm (42,125–58 cm⁻¹). The accurate Ritz wavelengths and calculated transition probabilities for forbidden lines in this paper are useful in the study and diagnostics of nebulae and other low-density astrophysical plasmas.

A spectral investigation of triply ionized gold (Au iv) has been carried out in the wavelength region of 500–2106 Å. The gold spectra were photographed at the National Institute of Standards and Technology, USA, on a 10.7 m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3 m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Our analysis is theoretically supported by the pseudorelativistic Hartree–Fock (HFR) formalism with a superposition of configuration interactions implemented in Cowan's suite of codes. Radiative transition parameters are also calculated using the HFR+CPOL (core polarization effects) model and the multiconfiguration Dirac–Hartree–Fock approach, and their comparisons are used to evaluate the transition rate data. All the previously reported levels of the 5d ⁸, 5d ⁷6s, and 5d ⁷6p configurations are confirmed, except one, and three are newly established. The missing ¹ S ₀ level of 5d ⁸ is now established at 55,277.8 cm⁻¹. A total of 981 observed lines (E1 type), classified to 1031 transitions, including 133 newly identified, enabled us to optimize 139 energy levels. Several astrophysically important transitions, forbidden (M1- and E2-type) lines of 5d ⁸ and 5d ⁷6s, are provided with their Ritz wavelengths and radiative parameters. A critically evaluated set of energy levels, observed and Ritz wavelengths along with their uncertainties, transition rates, and uniformly scaled intensities of Au iv lines have been presented. Also, large-scale atomic data to compute the opacity of Au iv in the kilonova ejecta have been supplemented in this work.

The spectral investigation of the triply ionized gold (Au IV) has been carried out in the wavelength region of 500--2106 Å. The gold spectra were photographed at the National Institute of Standards and Technology (NIST, USA) on a 10.7-m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3-m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Our analysis is theoretically supported by the pseudo-relativistic Hartree-Fock (HFR) formalism with superposition of configuration interactions implemented in Cowan's suite of codes. Radiative transition parameters are also calculated using HFR+CPOL (core-polarization effects) model and multiconfiguration Dirac-Hartree-Fock (MCDHF) approach, and their comparisons are used to evaluate the transition rate data. All the previously reported levels of the $5d^{8}$, $5d^{7}6s$, and $5d^{7}6p$ configurations are confirmed, except one and three are newly established. The missing $^{1}S_{0}$ level of $5d^{8}$ is now established at 55277.8 cm$^{-1}$. A total of 981 observed lines (E1-type) classified to 1031 transitions, including 133 newly identified, enabled us to optimize 139 energy levels. Several astrophysically important transitions, forbidden (M1- and E2-types) lines of $5d^{8}$ and $5d^{7}6s$, are provided with their Ritz wavelengths and radiative parameters. A critically evaluated set of energy levels, observed and Ritz wavelengths along with their uncertainties, transition rates, and uniformly-scaled intensities of Au IV lines have been presented. Also, large scale atomic data to compute opacity of Au IV in the kilonova ejecta have been supplemented in this work.