Observed hyperfine components of the N_J = 2₃−1₂ (left panels) and N_J = 3₄–2₃ (right panels) transitions of ¹³CCS, C¹³CS, and C¹³C³⁴S towards TMC-1. The abscissa corresponds to the rest frequency in MHz. 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 line) are derived from the LVG model described in Section 3 with n(H₂)=1.3×10⁴ cm⁻³ and the column densities given in Table 1 (see Section 4.3).