Production pathways of CCS and CCCS inferred from their 13C isotopic species

The rotational spectral lines (J(N) = 3(2)-2(1) and J(N) = 2(1)-1(0)) of (CCS)-C-13 and (CCS)-C-13 have been observed toward a cold dark cloud, TMC-1. The strongest hyperfine component lines of (CCS)-C-13 and (CCS)-C-13 (J(N) = 2(1)-1(0), F = 5/2-3/2) have successfully been detected. The [(CCS)-C-13]/[(CCS)-C-13] abundance ratio is determined to be 4.2 +/- 2.3 ( 3 sigma). The [CCS]/[(CCS)-C-13] ratio is evaluated to be 230 +/- 130 (3 sigma), and hence, (CCS)-C-13 is found to be significantly diluted. Such a difference between the (CCS)-C-13 and (CCS)-C-13 abundances is also found in L1521E, which is a very young core with rich carbon-chain molecules. Therefore, the anomaly is not specific to TMC-1, but seems to be common for the CCS-rich clouds. Furthermore, we have also observed the J = 4-3 transition of (CCCS)-C-13 and (CCCS)-S-34 in TMC-1 and L1521E and have found that the [(CCCS)-S-34]/[(CCCS)-C-13]ratio is larger than 8.4 ( 3 sigma). This lower limit is considerably larger than the interstellar [C-12][S-34]/[C-13][S-32] ratio of 3, indicating that (CCCS)-C-13 is diluted as in the case of (CCS)-C-13. These results give us strong constraints on the main pathways to produce CCS and CCCS.