The trend of consistent increases in laser power is often limited by the laser-induced damage threshold (LIDT) of the optic. Existing models have shown a link between the nonlinearv ionization rate at high intensities and LIDT. These models are extended to account for the presence of intermediate states and compared to laser calorimetric absorption (LCA) measurements of samples prepared with varying densities of intermediate states. Hafnia is well established for use in high LIDT optics due to its large band gap and high refractive index; however, a number of defect states can be induced by oxygen sub- or super-stoichiometry. The extended model shows good correlation to measurements of samples prepared with different densities of intermediate states.