One of the fundamental questions concerning the Milky Way Galaxy is its elemental composition and how this composition came about. It is believed that the original gas from which our Galaxy formed, consisted of entirely hydrogen and helium. Most of the heavier elements were formed since then by nucleosynthesis in stellar interiors and during stellar explosions. The aim of the research proposed here is to improve our under- standing of the origin and distribution of the chemical elements in our Galaxy. To this end, the Principal Investigator (PI) will focus on four distinct, but related projects: 1. Use abundance distribution curves for the Galaxy's halo stars to deduce the nature of the first generation of massive stars in the Galaxy and their nucleosynethesized products; 2. study the mixing of light elements (e.g., lithium, carbon, nitrogen, oxygen) in the convective envelopes of giant stars in the Galaxy's halo and disk; 3. use nebular absorption and emission lines of neutral gas in planetary nebulae to learn about the nuclear history of the precursor stars; and 4. take very high signal-to-noise spectra of diffuse interstellar bands towards selected, very lightly reddened lines of sight in order to obtain clues as to the bands'origin.
