Anomalous absorption in c-C3H and c-C3D radicals

摘要

Context.The c-C3H radical was first detected in TMC-1 by Yamamoto et al. (1987, ApJ, 322, L55), who observed the 212 → 111 transition at 91.5 GHz in emission. Mangum Wootten (1990, AA, 239, 319) observed the 110 → 111 transition at 14.8 GHz in emission in 12 additional galactic objects. Aims.The aim of this investigation is a quantitative estimate of relative line intensities under NLTE conditions. Methods.For wide ranges of physical parameters, where these molecules may be found, we have solved a set of statistical equilibrium equations coupled with the equations of radiative transfer in an on-the-spot approximation. For c-C3H, we accounted for 51 energy levels connected by 207 radiative transitions, and for c-C3D, we accounted for 51 energy levels connected by 205 radiative transitions. Results.Our results show that the 331 → 330 transition of c-C3H and c-C3D may be found in absorption against the cosmic microwave background (CMB). Furthermore, we found population inversion for the 110 111 transition. These findings may be useful in identifying these molecules in other cosmic objects, as well as for the determination of physical parameters in these objects.