IRC +10216 17.8GHz-26.3GHz spectrum

The identified lines are assigned to 18 different molecules and radicals. A total of 23 lines from species known to exist in this envelope are detected for the first time outside the Solar System and there are additional 20 lines firstly detected in IRC +10216. The potential orgin of U lines is also discussed.

Assuming local thermodynamic equilibrium (LTE), we determine rotational temperatures and column densities of 17 detected molecules. Molecular abundances relative to H_2_ are also estimated. A non-LTE analysis of NH_3_ shows that the bulk of its emission arises from the inner envelope with a kinetic temperature of 70+/-20K.

Evidence for NH_3_ emitting gas with higher kinetic temperature is also obtained, and potential abundance differences between various ^13^C-bearing isotopologues of HC_5_N are evaluated. Overall, the isotopic ^12^C/^13^C ratio is estimated to be 49+/-9. Finally, a comparison of detected molecules in the 1.3cm range with the dark cloud TMC-1 indicates that silicate bearing molecules are more predominant in IRC +10216.