Investigation of the Electronic Structure of PB and AsB using High Resolution Photoelectron Imaging of Cold PB⁻ and AsB⁻ Anions^†

We report a study on the electronic structure and chemical bonding of the PB and AsB diatomic molecules using high-resolution photoelectron imaging of cryogenically-cooled PB⁻ and AsB⁻ anions. The electron affinities of PB and AsB are measured to be 2.751(1) and 2.600(1) eV, respectively. The ground states of the PB⁻ and AsB⁻ anions are determined to be ²Σ⁺ with a σ¹π⁴ valence electron configuration. The ground states of neutral PB and AsB are found to be ³Π₂ with a σ¹π³ electron configuration. The spin-orbit excited states (³Π₁ and ³Π₀), as well as two low-lying singlet excited states (¹Σ⁺ and ¹Π), are observed. Unusual spectroscopic characteristics are observed in the ³Π₂ ground state of AsB, probably due to state mixing with a higher-lying ¹Δ₂ state. The current work provides extensive electronic and spectroscopic information for the PB and AsB molecules.