High-resolution photoelectron spectroscopy of vibrationally excited TiO2 anions

High-resolution photoelectron spectra of TiO2− excited to its v3=1 state were obtained via slow electron velocity-map imaging of cryogenically cooled anions (cryo-SEVI). To determine the ν3 (antisymmetric stretch) anion frequency, growth and depletion of various features in the cryo-SEVI spectrum were monitored over a range of infrared (IR) excitation energies. Photoelectron scans were taken at an IR pre-excitation energy of 918 cm−1 and yielded a ∼6% depletion of features in the ground state cryo-SEVI spectra as well as new hot and sequence bands based on the 310 and 311 transitions, respectively. By monitoring hot band intensities as a function of IR laser frequency, the rotational profile of the v3=0–1 transition was mapped out and found to be centered at 914(7) cm−1. The observed hot bands are Franck–Condon forbidden and arise from Herzberg–Teller coupling with the Ã1B2 neutral excited state, similar to what was observed in the cryo-SEVI spectra of TiO2−. The results from this IR cryo-SEVI experiment lay the groundwork for future investigations of larger bare and complexed transition metal–oxide clusters.