Planetary nebulae, the expelled outer envelopes of former AGB stars, provide a record of past stellar and Galactic chemical
evolution complementary to observational studies of AGB stars themselves. Nebular-derived element abundances are subject to
different systematics than those determined for stars, and different elements are observable in nebulae than in cool stellar
photospheres. In a planetary nebula, the star's initial composition has been modified by element transmutation reactions
during its luminous lifetime; the nebula is an explicit manifestation of the return of enriched stellar material to the ISM.
Recently infrared spectroscopy has opened up several new chapters in this story. I will discuss work by me and my
collaborators including the introduction of a robust method for determining true elemental Fe-group abundances in the
progenitor stars, and abundance determinations for trans-iron elements produced by slow neutron captures (the s-process)
during the AGB using newly identified infrared emission lines. These studies have the potential not only to constrain the
initial mass and metallicity of the progenitor, but also to distinguish among competing evolutionary models that make
different predictions for element production in AGB stars.
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