2018MNRAS.480.3397Y

Accurate line lists for the carbon dimer, C₂, are presented. These line lists cover rovibronic transitions between the eight lowest electronic states: X ¹Σ_g⁺, a ³Π_u, A ¹Π_u, b ³Σ_g^–, c ³Σ_u⁺, d ³Π_g, B ¹Δ_g, and B^′1Σ_g⁺. Potential energy curves (PECs) and transition dipole moment curves are computed on a large grid of geometries using the aug-cc-pwCVQZ-DK/MRCI level of theory including core and core-valence correlations and scalar relativistic energy corrections. The same level of theory is used to compute spin-orbit and electronic angular momentum couplings. The PECs and couplings are refined by fitting to the empirical (MARVEL) energies of ¹²C₂ using the nuclear-motion program DUO. The transition dipole moment curves are represented as analytical functions to reduce the numerical noise when computing transition line strengths. Partition functions, full line lists, Lande-factors, and lifetimes for three main isotopologues of C₂ (¹²C₂, ¹³C₂, and ¹²C¹³C) are made available in electronic form from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.