Electronic Structures and Photodetachment of TeO2−, TeO3−, and HTeO4− Anions: A Cryogenic Photoelectron Spectroscopic Study

Cryogenic anion photoelectron spectroscopy combined with quantum chemical calculations was employed to investigate the electronic structures and photodetachment properties of TeO2−, TeO3−, and HTeO4− anions. The adiabatic/vertical detachment energies (ADEs/VDEs) of these anions were determined through the photoelectron spectra at 193 nm, yielding values of 2.13/1.94, 4.20/3.64, and 5.64/5.20 eV, respectively. These results align well with the theoretical calculations and were further validated through Franck–Condon factor (FCF) simulations. TeO2− and TeO3− exhibit a notable multi-reference character, with TeO3− showing a pronounced structural change upon detachment from C3v to D3h geometry, leading to a substantial difference between its ADE and VDE. Orbital analyses of the photodetachment processes reveal a progressive shift in the primary contribution to the detached electron—from the Te atom to the O atoms—as the anion size increases. Moreover, a two-photon photodissociation–photodetachment process was identified for HTeO4−. These findings provide fundamental insights into the geometric and electronic structures of gas-phase tellurium oxides, offering a benchmark for further theoretical modeling and material development involving chalcogen oxide anions.