The low-lying electronic states of HfO2− and HfO2: A symmetry adapted cluster–configuration interaction (SAC-CI) study

Abstract

The low-lying doublet states of the HfO2− anion and low-lying triplet excited states of the HfO2 molecule were studied using the SAC-CI method. The vertical excitation spectrum of HfO2− was calculated. Four valence-bound states (X2A1, 12B1, 22A1, and 12B2(II)) and one dipole-bound state (2A1(DB)) of HfO2− were found. The vertical electron detachment energies (VDEs) from the ground electronic state of HfO2− to the triplet excited states of HfO2 were obtained. These VDEs were compared with previous photoelectron spectra of HfO2−, and possible candidate states for the unassigned bands were found. The equilibrium geometries of the valence-bound states of HfO2− and some selected triplet excited states of HfO2 were optimized. The adiabatic relative energies of these electronic states were obtained. Density functional theory (BPW91) was also applied to compute some electronic states of HfO2− and HfO2 for comparison.