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NASA NTRS · 20040088879

The HNC/HCN ratio in comets

Irvine, W. M.·Dickens, J. E.·Lovell, A. J.·Schloerb, F. P.·Senay, M.·Bergin, E. A.·Jewitt, D.·Matthews, H. E.·Ferris, J. P.
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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 in significant 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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NASA Discipline ExobiologyNon-NASA CenterMeteoroidsHydrogen Cyanide/analysis/chemistryCyanides/analysis/chemistryPhotochemistrySolar SystemSupport, U.S. Gov't, Non-P.H.SModels, ChemicalAstronomyExtraterrestrial EnvironmentIsomerism

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Irvine, W. M., Dickens, J. E., Lovell, A. J., Schloerb, F. P., Senay, M., Bergin, E. A., Jewitt, D., Matthews, H. E., Ferris, J. P.. 1997-01-01. The HNC/HCN ratio in comets. https://ntrs.nasa.gov/citations/20040088879

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