Vibrational Resolved Photoelectron Imaging and Theoretical Study of the Group IVB Transition Metal Oxides Anions: MO₂⁻ (M= Ti, Zr, and Hf)^†

The vibrational resolved spectra of MO₂⁻/MO₂ (M=Ti, Zr, and Hf) are reported by using photoelectron imaging and theoretical calculations. The results indicate that all the ground states of anionic and neutral MO₂ (M= Ti, Zr, and Hf) compounds are formed in bent insertion structures. The observed ground-state adiabatic detachment energy (ADE) is measured to be 1.597±0.003, 1.651±0.003, and 2.119±0.003 eV for TiO₂⁻, ZrO₂⁻, and HfO₂⁻, respectively. The vibrational frequencies of the anionic and neutral MO₂ are also determined from the experimental spectra. The results of theoretical calculations show that the electronic configurations of MO₂⁻ are ²A₁ with C_2v point group. Bond order analysis indicates that the two M−O bonds are all multiple characters.