Observed lines of HCCS (panel a) and NCS (panels b and c) towards TMC-1. The abscissa corresponds to the rest frequency assuming a local standard of rest velocity of the source of 5.83 km s⁻¹ (see text). Blanked channels correspond to negative features produced in the frequency switching data folding. The ordinate is the antenna temperature corrected for atmospheric and telescope losses in milliKelvin. Spectral resolution is 38.15 kHz. The red lines show the synthetic spectrum of HCCS and NCS for a rotational temperature of 5 K, a linewidth of 0.6 km s⁻¹, and a column density of 6.8 × 10¹¹ cm⁻² and 7.8 × 10¹¹ cm⁻², respectively.