Revised and extended analysis of the fourth spectrum of indium: In IV

- Indium spectra were recorded on 3-m and 10.7-m spectrographs with a triggered spark.
- Calculations with superposition of configurations and relativistic corrections.
- New atomic transitions of In IV were identified to establish new energy levels.
- Weighted oscillator strength log(gf) and transition probability(gA) were calculated.
- Ionization potential of In IV was determined experimentally.

The spectrum of triply ionized indium (In IV) has been investigated in the wavelength region 245-4443 Å. The In3+ is a Pd-like ion with the ground configuration 4p64d10. All levels of the low lying excited configurations 4d95p, 4d9ns (n=5-7), 4d95d and 4d85s2 have been reported earlier, while for the higher configurations 4d9np (n=6,7) and 4d9nf (n=4-11), only the J=1 levels radiatively decaying to the ground level have been reported. The present work extends the analysis to include the 4d96p, 4d96d, 4d94f and 4d95f configurations. A total 116 levels have been established, 56 of them being new. All the previously reported levels have been confirmed except 4d97s 3D1, 4d97p 3P1, 4d96f 3P1 and 4d85s23P1. The experimental data for the present work was recorded on a 3-m normal incidence spectrograph of St. Francis Xavier University, Antigonish (Canada), as well as on the 10.7 m normal and grazing incidence spectrographs of the National institute of Standards and Technology, Gaithersburg (USA). In both laboratories, a triggered spark source was used. The wavelengths above 2000 Å were supplemented from Bhatia's thesis where an electrodeless discharge source was used. Theoretical predictions were made using Cowan's Hartree-Fock-relativstic atomic codes with superposition of configurations. Least squares fitted (LSF) parametric calculations were used to interpret the energy levels. For vacuum ultraviolet wavelength region our wavelength accuracy is ±0.005 Å. We estimate the ionization potential of In IV to be 450,921.7±86.0 cm−1 (55.9072±0.0106 eV).