Spectroscopic Constants and Vibrational Frequencies for l-C3H+ and Isotopologues from Highly Accurate Quartic Force Fields: The Detection of l-C3H+ in the Horsehead Nebula PDR Questioned
Abstract
Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C3H+. In an effort to corroborate this finding, we employed state-of-the-art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in the rotational transition energies resulting from this difference in D on the order of 1 MHz for the lowest observed transition (J = 4 → 3) and growing as J increases, the assignment of the observed rotational lines from the Horsehead nebula to l-C3H+ is questionable.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2013
- DOI:
- 10.1088/2041-8205/768/2/L25
- arXiv:
- arXiv:1305.1658
- Bibcode:
- 2013ApJ...768L..25H
- Keywords:
-
- astrochemistry;
- ISM: individual objects: Horsehead nebula;
- ISM: lines and bands;
- ISM: molecules;
- molecular data;
- radio lines: ISM;
- Astrophysics - High Energy Astrophysical Phenomena;
- Physics - Chemical Physics
- E-Print:
- Huang, X., Fortenberry, R. C., &