Improved Line Data for the Swan System (Cc)-C-12-C-13 Isotopologue

Abstract

We present new, accurate predictions for rotational line positions, excitation energies, and transition probabilities of the (CC)-C-12-C-13 isotopologue Swan d(3)Pi-a(3)Pi system 0-0, 0-1, 0-2, 1-0, 1-1, 1-2, 2-0, 2-1, and 2-2 vibrational bands. The line positions and energy levels were predicted through new analyses of published laboratory data for the (CC)-C-12-C-13 lines. Transition probabilities were derived from recent computations of transition dipole moments and related quantities. The (CC)-C-12-C-13 line data were combined with similar data for C-12(2), reported in a companion paper, and applied to produce synthetic spectra of carbon-rich metal-poor stars that have strong C-2 Swan bands. The matches between synthesized and observed spectra were used to estimate band head positions for a few of the (CC)-C-12-C-13 vibrational bands and to verify that the new computed line data match observed spectra. The much weaker C-2 lines of the bright red giant Arcturus were also synthesized in the band head regions.