Infrared Spectroscopy of the ν 3 Band of Hydrogen Cyanide in Comet C/1995 O1 Hale–Bopp

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 1999, Vol.142 (2), p.498-508
• Main Authors: Magee-Sauer, Karen, Mumma, Michael J., DiSanti, Michael A., Russo, Neil Dello, Rettig, Terrence W.
• Format: Article
• Language: English
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1006/icar.1999.6215

Hydrogen cyanide (HCN) was detected in Comet Hale–Bopp at infrared wavelengths near 3.0 μm on four dates between Feb 24.0 and May 1.0 1997 using high-resolution spectroscopy. The average rotational temperature retrieved for the (001) vibrational level on UT 1997 April 29.9 was (95±6) K near the nucleus, increasing to (122±8) K in the intermediate coma (4″–10″ off the nucleus). The HCN production rate on April 29.9 was (3.09±0.13)×10 28 molecules s −1. When compared with the water production rate obtained from direct measurements of the H 2O 100-010 band on common observation dates using the same instrument and data processing algorithms, the weighted average (for the four dates) of the relative abundance (HCN/H 2O) was (0.40±0.05)%. The measured spatial distribution for HCN is consistent with its release at the nucleus—no significant contribution from a distributed source is required within 10,000 km of the nucleus.