Photoelectron Imaging Spectroscopy of ZrO^- Diatomic Anion

The diatomic ZrO^- anion has been prepared by laser ablation and studied by photoelectron imaging spectroscopy combined with quantum chemistry calculations. The observed photoelectron spectra can be well assigned on the basis of reported optical spectroscopy and high-level ab initio calculations. The ground state of ZrO^- is a ²△ state with spin-orbit splitting of 578±12 cm^-. The electron affinity of ZrO is 1.249±0.005 eV. For the first time, the c³Σ^- state of ZrO has been experimentally observed at 13316±24 cm^- with respect to the X¹∑⁺ ground state. A comparison between ZrO and the isoelectronic molecule NbN has been made.