Non-LTE modelling of the HC₂NC and HNC₃abundance in astrophysical environments

The isomers of HC 3 N, namely 2 NC and HNC , are widely observed in the interstellar medium circumstellar envelopes. Their abundance has been determined under assumption local thermodynamic equilibrium (LTE) conditions or non-LTE radiative transfer models, but considering collisional excitation N as same for all isomers. Chemical models prototypical cold cores, TMC-1 L1544, reproduced fairly well, they tend to overestimate abundances with respect observations. It is therefore worth revisiting interpretation observational spectra these using a rigorous modelling. were then calculations based on proper rate coefficients first time this work. Modelling brightness temperature when their collision shows that LTE approximate data may lead deviations up factor ~1.5. Reinterpreting led us significant differences relative previously determined. Our findings suggest quite similar ratios L1544 cores well L483 protostar. This work will encourage further modelling more robust future studies revisit chemistry its molecular clouds.