2008ApJS..177..275H

We present the results of our spectral line surveys in the 1.3 and 2 mm windows toward the carbon-rich envelope of IRC +10216. There were 377 lines are detected in total, of which 360 lines are assigned to 57 known molecules (including 29 rare isotopomers and two cyclic isomers). Only 17 weak lines remain unidentified. Rotational lines of isotopomers ¹³CCH and HN¹³C are detected for the first time in IRC +10216. The detection of the formaldehyde lines in this star is also confirmed. Possible abundance differences among the three ¹³C-substituted isotopic isomers of HC₃N is reported. Isotopic ratios of C and O are confirmed to be nonsolar while those of S and Si to be nearly solar. Column densities have been estimated for 15 molecular species. Modified spectroscopic parameters have been calculated for NaCN, Na¹³CN, KCN, and SiC₂. Transition frequencies from the present observations were used to improve the spectroscopic parameters of Si¹³CC, ²⁹SiC₂, and ³⁰SiC₂.