CIT 6 and IRC+10216 30-50GHz spectra

We applied the rotational-diagram method to derive rotational temperatures and column densities for HC_5_N and HC_7_N. For other molecules, we assumed an excitation temperature to derive their column densities. Molecular column densities in CIT~6 are systematically lower than those in IRC+10216, typically by about one order of magnitude.

Silicon- and sulfur-bearing species such as SiS and CS show the strongest depletion, whereas carbon-chain molecules (HC_n_N, C_6_H) remain relatively prominent, indicating that carbon-chain formation is still efficient in CIT 6. Rotational temperatures are higher in CIT 6, consistent with emission arising from warmer and more compact regions of its envelope. Both sources show low ^12^C/^13^C ratios and mildly sub-solar ^28^Si/^29^Si values, indicating non-solar isotopic compositions.

Both envelopes display canonical carbon-rich AGB chemistry and comparable isotopic compositions. CIT 6, however, shows slightly higher excitation temperatures, stronger carbon-chain growth, and deeper depletion of Si- and S-bearing species. These signatures point to a more evolved circumstellar environment, where dust condensation and shock processing further modulate the molecular composition.