A combined ab initio and Franck-Condon factor simulation study on the photodetachment spectrum of HfO₂^-

Restricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the X̃1A1state of HfO2and the X̃2A1state of HfO2-were computed, employing the quasi-relativistic effective core potential, ECP60MWB, and an associated contracted [13s6p6d4f3g2h] basis set designed for Hf, and the augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set for O. Based on the differences between the computed r0and regeometrical parameters obtained from the PEF, and available experimentally derived r0geometrical parameters of the X̃1A1state of HfO2, the experimental regeometrical parameters of the X̃1A1state of HfO2were estimated as:-re(HfO) = 1.7751 Å and θe(OHfO) = 107.37°. In addition, Franck-Condon factors for the HfO2(X̃1A1) + e ← HfO2-(X̃2A1) electron detachment process, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the HfO2(X̃1A1) + e← HfO2-(X̃2A1) photodetachment band of HfO2-. Employing the estimated experimental regeometrical parameters of the X̃1A1state of HfO2obtained in this work, the iterative Franck-Condon analysis (IFCA) procedure was carried out to optimize the geometrical parameters of the X̃2A1state of HfO2-until the simulated spectrum matched best with the experimental 355 nm photodetachment spectrum of W. Zheng, et. al., J. Phys. Chem. A, 1998, 102, 9129. The equilibrium geometrical parameters of X̃2A1state of HfO2-derived via the IFCA procedure are re(HfO) = 1.823 Å and θe(OHfO) = 111.5°. Further calculations on low-lying triplet states of HfO2gave adiabatic electronic energies (Te's) of, and vertical excitation energies (Tvert's) to, the ã3B2, b̃3B1, c̃3A1and d̃3A2states of HfO2(from the X̃1A1state of HfO2), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the X̃2A1state of HfO2-.