Low-lying Dipole Resonances in FeCN^-: A Viable Formation Pathway for FeCN^-in Space

A low-lying resonance in FeCN- anion was identified through abrupt changes in the spectral dependence of the photoelectron angular distribution. Non-Franck-Condon transitions from the resonance to the neutral FeCN (4 "), and the corresponding photoelectron angular distributions revealed that the resonance is a dipole scattering state. Significant thermionic electron emission was observed in the resonant photoelectron spectra, indicating a strong coupling of the resonance with the ground state of this triatomic anion and its competition over autodetachment. This low-lying resonance is identified to be an efficient pathway for the formation of FeCN- anion in the outer envelope of IRC+10216. The results in general reveal formation pathways in space for anions with low-lying resonances and large permanent dipole moment.