Negative ion photoelectron spectroscopy of PN: electron affinity and electronic structures of PN˙.

We report here a negative ion photoelectron spectroscopy (NIPES) and study of the recently synthesized planar aromatic inorganic ion PN, to investigate the electronic structures of PN and its neutral PN˙ radical. The adiabatic detachment energy of PN (electron affinity of PN˙) was determined to be 3.765 ± 0.010 eV, indicating high stability for the PN anion. electronic structure calculations reveal the existence of five, low-lying, electronic states in the neutral PN˙ radical. Calculation of the Franck-Condon factors (FCFs) for each anion-to-neutral electronic transition and comparison of the resulting simulated NIPE spectrum with the vibrational structure in the observed spectrum allows the first four excited states of PN˙ to be determined to lie 6.2, 6.7, 11.5, and 22.8 kcal mol above the ground state of the radical, which is found to be a 6π-electron, A, σ state.