Laboratory detection of four isomers of C5H2 molecule
have been reported by Travers et al. ([CITE]), McCarthy et al. ([CITE]), and
Gottlieb et al. ([CITE]). They suggested for detection of the ring-chain
isomer of C5H2 (c-C5H2) in cosmic objects, as it is the most stable one in
comparison to the others. Two transitions 313−212 and 303−202 at 19.147 GHz and 19.606 GHz, respectively, of c-C5H2
have been detected in TMC-1. We suggest that the c-C5H2 may be
identified in cool cosmic objects through its transition 313−404
at 4.3 GHz in absorption against the cosmic microwave background.
Since in absence of availability of the collisional rates, we have used scaled
values for them, we have checked the sensitivity of the lines on the rates by
enhancing the rate for the transitions with Δka=0 by a factor of 10.
transitions are not found sensitive, our results may be treated as qualitative
in nature. This absorption line may play an important
role for identification of c-C5H2 in cosmic objects