Knowledge Bank

The circumstellar cloud of the late-type star IRC+10216 contains many molecules expected in a carbon-rich environment. In the infrared these are seen in absorption against the hot star and dense inner dust. During the past few years we have been studying the high resolution spectrum in this star at 12-14 microns. This region is dominated by $C2H2$ absorption lines, and also contains strong lines of $HCN.1$ This effort has culminated recently in the identification of the $v=0-l$ band of SiS, the first infrared detection of this molecule. Intensities and lineshapes in these spectra probe the temperature, composition and chemistry in the circumstellar envelope. Our high resolution observations in the thermal infrared are performed with a cryogenic postdisperser coupled to the FTS at the 4-meter telescope at Kill Peak. The $postdisperser2$ acts as a narrow bandwidth cold filter. thereby reducing the noise caused by radiation at the detector. The FTS produces resolutions as high as $0.01cm-1$. the best presently achieved in this spectral region