ExoMol line lists XXXI: Spectroscopy of lowest eights electronic states of C2

Abstract

Accurate line lists for the carbon dimer, C2, are presented. These line lists cover rovibronic transitions between the eight lowest electronic states: X 1Σg+, a3∏u, A1∏u, b3Σg-, c3Σu+ d3∏g, B1Δg, and B' 1Σg+. 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, Landé-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.