We report Shanghai Tian Ma Radio Telescope detections of several long carbon-chain molecules at C and Ku band , including HC _ { 3 } N , HC _ { 5 } N , HC _ { 7 } N , HC _ { 9 } N , C _ { 3 } S , C _ { 6 } H and C _ { 8 } H toward the starless cloud Serpens South 1a .
We detected some transitions ( HC _ { 9 } N J =13-12 F =12-11 and F =14-13 , H ^ { 13 } CCCN J =2-1 F =1-0 and F =1-1 , HC ^ { 13 } CCN J =2-1 F =2-2 , F =1-0 and F =1-1 , HCC ^ { 13 } CN J =2-1 F =1-0 and F =1-1 ) and resolved some hyperfine components ( HC _ { 5 } N J =6-5 F =5-4 , H ^ { 13 } CCCN J =2-1 F =2-1 ) for the first time in the interstellar medium .
The column densities of these carbon-chain molecules in a range of 10 ^ { 12 } -10 ^ { 13 } cm ^ { -2 } are comparable to two carbon-chain molecule rich sources , TMC-1 and Lupus-1A .
The abundance ratios are 1.00 : ( 1.11 \pm 0.15 ) : ( 1.47 \pm 0.18 ) for [ H ^ { 13 } CCCN ] : [ HC ^ { 13 } CCN ] : [ HCC ^ { 13 } CN ] .
This result implies that the ^ { 13 } C isotope is also concentrated in the carbon atom adjacent to the nitrogen atom in HC _ { 3 } N in Serpens south 1a , which is similar to TMC-1 .
The [ HC _ { 3 } N ] / [ H ^ { 13 } CCCN ] ratio of 78 \pm 9 , the [ HC _ { 3 } N ] / [ HC ^ { 13 } CCN ] ratio of 70 \pm 8 , and the [ HC _ { 3 } N ] / [ HCC ^ { 13 } CN ] ratio of 53 \pm 4 are also comparable to those in TMC-1 .
In any case , Serpens South 1a proves a testing ground for understanding carbon-chain chemistry .