The Chemistry of Population III Supernova Ejecta: I - Formation of
  Molecules in the Early Universe
  We study the formation and destruction of molecules in the ejecta of
Population III supernovae (SNe) using a chemical kinetic approach to follow the
evolution of molecular abundances from day 100 to day 1000 after explosion. The
chemical species included range from simple di-atomic molecules to more complex
dust precursor species. All relevant chemical processes that are unique to the
SN environment are considered. Our work focuses on zero-metallicity progenitors
with masses of 20, 170, and 270 Msun, and we study the effect of different
levels of heavy element mixing and the inward diffusion of hydrogen on the
ejecta chemistry. We show that the ejecta chemistry does not reach a steady
state within the relevant time-span for molecule formation. The primary species
formed are O2, CO, SiS, and SO. The SiO, formed as early as 200 days after
explosion, is rapidly depleted by the formation of silica molecular precursors
in the ejecta. The rapid conversion of CO to C2 and its thermal fractionation
at temperatures above 5000 K allow for the formation of carbon chains in the
oxygen-rich zone of the unmixed models, providing an important pathway for the
formation of carbon dust in hot environments where the C/O ratio is less than
1. We show that the fully-mixed ejecta of a 170 Msun progenitor synthesizes
11.3 Mun of molecules whereas 20 Msun and 270 Msun progenitors produce 0.78,
and 3.2 Msun of molecules, respectively. The admixing of 10 % of hydrogen into
the fully-mixed ejecta of the 170 Msun progenitor increases its molecular yield
to ~ 47Msun. The unmixed ejecta of a 170 Msun progenitor supernova without
hydrogen penetration synthesizes ~37 Msun of molecules, whereas its 20 Msun
counterpart produces ~ 1.2 Msun. Finally, we discuss the cosmological
implication of molecule formation by Pop. III SNe in the early universe.
