Figure 4: Oscillator strength of interband transitions.
From: The refractive index and electronic gap of water and ice increase with increasing pressure
The imaginary part of the electronic dielectric constant of water, 
2 multiplied by the cell volume V as a function of frequency ω at ~1 and ~10 GPa and 1,000 K. Eg labels the frequencies corresponding to the band gaps of water at ~1 and ~10 GPa, respectively.
