Characterization of the vibrational properties of copper difluoride anion and neutral ground states via direct and indirect photodetachment spectroscopy

Photoelectron spectra of ⁶³CuF₂ ⁻ are reported at wavelengths 310 nm, 346.6 nm, and 350.1 nm, obtained via velocity map imaging. The photoelectron angular distributions allow for the unambiguous assignment of a ²Σ_g ⁺ neutral CuF₂ ground state. Vibrational analysis of the direct detachment transitions in the spectra enables accurate determination of the anion and neutral bond length difference (0.073 Å), adiabatic electron affinity of CuF₂ (3.494 eV) and symmetric stretching (500 cm⁻¹, anion, and 630 cm⁻¹, neutral) and antisymmetric stretching (610 cm⁻¹, anion, and 782 cm⁻¹ neutral) frequencies of the ground electronic states. Strongly photon energy dependent intensities are also observed for select transitions. Equation-of-motion coupled-cluster singles and doubles calculations augmented by a complex absorbing potential reveal a metastable ¹Π_g anion state which is optically accessible due to Renner-Teller coupling. Mediation of the detachment process by this state allows measurement of the bending frequencies (177 cm⁻¹, anion, and 200 cm⁻¹, neutral) completing the inventory of experimentally measured vibrational properties of the ground electronic states.