Molecular rotational contour fitting of ultra-high-resolution profiles of diffuse interstellar bands

The first application of molecular rotational contour fitting to the analysis of high-resolution profiles of the λλ6614 and 5797 diffuse interstellar absorption bands is described. A range of selected molecular, electronic and transition dipole symmetries is considered. It is found that the profile of λ6614 is well reproduced by a Coriolis-induced perpendicular electronic transition of a planar oblate symmetric top molecule. Based on this result and other considerations, large carbon ring molecules emerge as good candidates for the carriers of the λ6614 and (possibly) λ5797 bands. Molecular constants, molecular rotational temperatures and linewidth parameters consistent with the observational data for λ6614 are reported and compared with those anticipated for candidate diffuse band carriers and with astronomical data obtained from studies of molecules in the same lines of sight. Some discrepancies between observed and fitted profiles are noted.