Radiative electron attachment to rotating C$_3$N through dipole-bound states

The role of a large dipole moment in rotating neutral molecules interacting with low-energy electrons is studied using an accurate {\it ab initio} approach accounting for electronic and rotational degrees of freedom. It is found that theory can reproduce weakly-bound (dipole-bound) states observed in a recent photodetachment experiment with C$_3$N$^-$ [Phys. Rev. Lett. {\bf 127}, 043001 (2021)]. Using a similar level of theory, the cross section for radiative electron attachment to the C$_3$N molecule, forming the dipole-bound states, was determined. The obtained cross section is too small to explain the formation of C$_3$N$^-$ in the interstellar medium, suggesting that it is likely formed by a different process.