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We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations ofdistorted-wave photoionization (PI) cross sections, and total and partialfinal-state resolved radiative recombination (RR) and dielectronicrecombination (DR) rate coefficients for the first six ions of the trans-ironelement Se. These calculations were motivated by the recent detection of Seemission lines in a large number of planetary nebulae. Se is a potentiallyuseful tracer of neutron-capture nucleosynthesis, but accurate determinationsof its abundance in photoionized nebulae have been hindered by the lack ofatomic data governing its ionization balance. Our calculations were carried outin intermediate coupling with semi-relativistic radial wavefunctions. PI andrecombination data were determined for levels within the ground configurationof each ion, and experimental PI cross-section measurements were used tobenchmark our results. For DR, we allowed dn=0 core excitations, which areimportant at photoionized plasma temperatures. DR is the dominant recombinationprocess for each of these Se ions at temperatures representative ofphotoionized nebulae (~10^4 K). To estimate the uncertainties of these data, wecompared results from three different configuration-interaction expansions foreach ion, and tested the sensitivity of the results to the radial scalingfactors in the structure calculations. We find that the internal uncertaintiesare typically 30-50% for the direct PI cross sections and ~10% for the computedRR rate coefficients, while those for low-temperature DR can be considerablylarger (from 15-30% up to two orders of magnitude) due to the unknown energiesof near-threshold autoionization resonances. The results are suitable forincorporation into photoionization codes used to numerically simulateastrophysical nebulae, and will enable robust determinations of nebular Seabundances.

Atomic data for neutron-capture elements I. Photoionization and recombination properties of low-charge selenium ions