On Benzene in the Circumstellar Envelopes

J. Cernicharo, A. M. Heras, A. G. G. M. Tielens, J. R. Pardo, F. Herpin, M. Guélin, and L. B. F. M. Waters,
Infrared Space Observatory's Discovery of C4H2, C6H2, and Benzene in CRL 618
Astrophys. J. 546, L123–L126 (2001);
report the detection of the ν4 band of benzene with an origin at 674.0 cm–1 (or 14.84 μm) employing mid-infrared spectroscopy. The band is clearly observed, but not particularly strong. Unfortunately, possible rotational substructure, including that from hot-band, may be present, but is near the noise limit as pointed out by the authors. The derived abundances seem plausible. Moreover, the PAH hypothesis, which most astronomers accept with little caution, if any, requires the presence of benzene in such environments, as probably do the recently reported rather secure detections of C60 and C70. Finally, there does not seem to be any alternative assignment for this feature. Overall, one can probably view the detection of benzene as, at least, fairly secure, but a small degree of caution may be useful.

Contributor(s): H. S. P. Müller; 10, 2003; modified 1, 2011