Observed transitions of CCCS, CCC³⁴S, ¹³CCCS, and C¹³CCS towards TMC-1. All transitions of CCCS are shown in the left panels. The right panels show J=6–5, 7–6, and 8–7 of the three isotopologues. The abscissa corresponds to the local standard of rest velocity of the lines adopting the rest frequencies given in Table B.1. The ordinate corresponds to the antenna temperature corrected for atmospheric and telescope losses in mK. The derived line parameters are given in Table B.1. The synthetic spectra (red lines) have been calculated from the LVG model described in Section 4.4. The adopted volume density is n(H₂)=1.3×10⁴ cm⁻³ for all isotopologues, and the resulting column densities are given in Table 1.