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

Abstract

The first application of molecular rotational contour fitting to the analysis of high-resolution profiles of the lambda lambda 6614 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 lambda 6614 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 lambda 6614 and (possibly) lambda 5797 bands. Molecular constants, molecular rotational temperatures and linewidth parameters consistent with the observational data for lambda 6614 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.