Detectable interstellar anions: Examining the key factors

Electron attachment energy (eAE) and the dipole moment of the neutral molecules are related to the radiative electron attachment (REA) process, which is an important formation route of interstellar anions under various astrophysical environments. Electron attachment energies (eAEs) have been calculated for over 80 carbon chain neutral molecules; C_n, C_nX (X = N, O, S, H, Si, P), HC_nN using ab initio quantum chemical method. Dipole moments of these neutral species and those of their corresponding anions are also theoretically estimated. The anions are found to be significantly more stable than their corresponding neutral analogues in most of the carbon chains considered. The high eAEs and the large dipole moment of most of the neutral species suggest a high detectability of their corresponding anions in the interstellar medium if they are abundant. Members of the C_2nO^-, C_2nS^-, C_2n1Si, HC_2nN^-, C_nP^-, and C_2n chains with increasing n are good candidates for future astronomical detection including the higher members of the C_2nH^- and C_2n-1N^- groups whose lower members have been observed.