High Resolution Infrared Spectroscopy of Comet Hale-Bopp
T.Y. Brooke (JPL), H.A. Weaver (JHU), G. Chin (NASA/GSFC), S.J. Kim (Kyunghee U.)
High resolution spectra of comet Hale-Bopp (C/1995 O1) in the 2-5 
m
region obtained during UT 2-5 March 1997 revealed emission lines
of the gas-phase molecules CH 
, C 
H 
, HCN, C H , H O,
and CO. The spectra were obtained at the NASA Infrared Telescope
Facility, Mauna Kea, Hawaii, using CSHELL, an imaging spectrometer
with a spectral resolving power of 
. The
comet's heliocentric and geocentric distances were 1.0 AU and 1.5AU,
respectively, on 2 March.
Based on a preliminary analysis of spectra taken near 3.0 m on 2
March, the P8-P11 lines of HCN and the P7 line of C H have been
detected. The estimated rotational temperature of HCN is 
K, which we assume is valid for C H as well. Estimated
production rates at the nucleus were 
sec 
for both molecules. Using a water production rate of 
sec on 1.8 March, calculated from infrared
emission lines (Dello Russo et al. IAUC 6604, 26 March 1997), we
derive relative abundances of 
% with respect to water
for both HCN and C H .
OH lines were also detected and NH lines were probably present.
In addition, there was an emission feature which we have not yet
identified at a rest wavenumber of 3286.57 cm , which was also
present in Hyakutake.