Abstract
The abundance ratio of the isomers HCN and HNC has been investigated in comet Hale-Bopp (C/1995 O1) through observations of the J = 4−3 rotational transitions of both species for heliocentric distances 0.93 < r < 3 AU, both pre- and post-perihelion. After correcting for the optical depth of the stronger HCN line, we find that the column density ratio of HNC/HCN in our telescope beam increases significantly as the comet approaches the Sun. We compare this behavior to that predicted from an ion-molecule chemical model and conclude that the HNC is produced insignificant measure by chemical processes in the coma; i.e., for comet Hale-Bopp, HNC is not a parent molecule sublimating from the nucleus.
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Irvine, W.M., Dickens, J.E., Lovell, A.J. et al. The HNC/HCN Ratio in Comets. Earth, Moon, and Planets 78, 29–35 (1997). https://doi.org/10.1023/A:1006202823878
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DOI: https://doi.org/10.1023/A:1006202823878