Dicarbon formation in collisions of two carbon atoms

Radiative association cross sections and rates are computed, using a quantum approach, for the formation of C₂ molecules (dicarbon) during the collision of two ground state C(³P) atoms. We find that transitions originating in the C ¹Π_g, d ³Π_g, and 1⁵Π_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.