Atomic Data and Nuclear Data Tables

We identify [Se III] 1.0994 µm in the planetary nebula (PN) NGC 5315 and [Kr VI] 1.2330 µm in three PNe, from spectra obtained with the FIRE spectrometer on the 6.5-m Baade Telescope. Se and Kr are the two most widely-detected neutron-capture elements in astrophysical nebulae, and can be enriched by s-process nucleosynthesis in PN progenitor stars. The detection of [Se III] 1.0994 µm is particularly valuable when paired with observations of [Se IV] 2.2858 µm, as it can be used to improve the accuracy of nebular Se abundance determinations, and allows Se ionization correction factor (ICF) schemes to be empirically tested for the first time. We present new effective collision strength calculations for Se 2+ and Kr 5+ , which we use to compute ionic abundances. In NGC 5315, we find that the Se abundance computed from Se 3+ /H + is lower than that determined with ICFs that incorporate Se 2+ /H +. We compute new Kr ICFs that take Kr 5+ /H + into account, by fitting correlations found in grids of Cloudy models between Kr ionic fractions and those of more abundant elements, and use these to derive Kr abundances in four PNe. Observations of [Se III] and [Kr VI] in a larger sample of PNe, with a range of excitation levels, are needed to rigorously test the ICF prescriptions for Se and our new Kr ICFs.

In this paper, we present results of experimental determination of Stark parameters of Ar II
spectral lines. We report 126 half-width and 111 shift results, 53 half-widths and 44 shifts
of which are presented here for the first time. The obtained data may be of astrophysical
interest. The results were compared with available experimental results of other authors and
with calculated ones in the cases where it was possible. A low-pressure pulsed arc, filled with
pure argon, was used as a plasma source. All measurements were done under electron density
which ranges from 0.20 × 1023 to 1.15 × 1023 m−3 and electron temperature from 16 000 to
26 000 K.