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 2Σg+ 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 1Πg 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.