Dicarbon formation in collisions of two carbon atoms
  Radiative association cross sections and rates are computed, using a quantum
approach, for the formation of C$_2$ molecules (dicarbon) during the collision
of two ground state C($^3$P) atoms. We find that transitions originating in the
C$\;^1\Pi_g$, d$\;^3\Pi_g$, and 1$\;^5\Pi_u$ states are the main contributors
to the process. The results are compared and contrasted with previous results
obtained from a semi-classical approximation. New ab initio potential curves
and transition dipole moment functions have been obtained for the present work
using the multi-reference configuration interaction approach with the Davidson
correction (MRCI+Q) and aug-cc-pCV5Z basis sets, substantially increasing the
available molecular data on dicarbon. Applications of the current computations
to various astrophysical environments and laboratory studies are briefly
discussed focusing on these rates.
