Hyperfine Structure Identification of Interstellar Cyanoallene Toward TMC-1

Published

January 10, 2006

Author(s)

Francis J. Lovas, A Remijan, J M. Hollis, P R. Jewell, Lewis E. Snyder

Abstract

Interstellar cyanoallene (CH2CCHCN) has been detected with the 100-m Green Bank Telescope (GBT) toward the dark Taurus Molecular Cloud (TMC-1) by means of the 414-313, 404-303, 515 -414, and 505-404 rotational transitions at 20.2 GHz, 20.6 GHz, 25.2 GHz, and 25.7 GHz, respectively. The hyperfine structure (hfs) of the 414-313 transition is resolved; the remaining transitions have hfs components that are blended but are inferred owing to linewidth excesses atypical of TMC-1. An analysis of these four rotational transitions yields an average column density NT = 2.0(5) x 1012 cm-2 at an assumed rotational temperature of 4 K. The cyanoallene isomer methylcyanoacetylene (CH3CCCN) has previously been observed in TMC-1 and found to have a rotational temperature of ~4 K by other investigators. Using the GBT, the K = 0 and K=1 structure of the JK = 5K - 4K transition of methylcyanoacetylene was resolved toward TMC-1 and a total column density of NT = 4.5(4) x 1011 cm-2 was obtained for the 4 K rotational temperature. Thus, cyanoallene appears to be more abundant than methylcyanoacetylene toward TMC-1 by a factor of ~4.5. The implications of this result are discussed in terms of relative bonding energy differences and possible differences in formation chemistry.

Citation

Astrophysical Letters & Communications

Pub Type

Journals

Keywords

abundances, cyanoallene, interstellar molecule, methylcyanoacetylene, microwave spectrum, radio astronomy, Taurus Molecular

Citation

Lovas, F. , Remijan, A. , Hollis, J. , Jewell, P. and Snyder, L. (2006), Hyperfine Structure Identification of Interstellar Cyanoallene Toward TMC-1, Astrophysical Letters & Communications (Accessed November 3, 2025)