Neutron ( n ) -capture elements ( atomic number Z > 30 ) , which can be produced in planetary nebula ( PN ) progenitor stars via s -process nucleosynthesis , have been detected in nearly 100 PNe .
This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements .
However , significant challenges must be addressed before this goal can be achieved .
One of the most substantial hurdles is the lack of atomic data for n -capture elements , particularly that needed to solve for their ionization equilibrium ( and hence to convert ionic abundances to elemental abundances ) .
To address this need , we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr .
The calculations were benchmarked against experimental photoionization cross section measurements .
In addition , we computed charge transfer ( CT ) rate coefficients for ions of six n -capture elements .
These efforts will enable the accurate determination of nebular Se and Kr abundances , allowing robust investigations of s -process enrichments in PNe .