THz spectroscopy of ice

We have shown that the THz-time-domain spectroscopy technique can be used to measure accurately the refractive indices of crystalline ice in the THz range. Our 0.25-1.0 THz results bridge the gap between the microwave and the far IR regions. They agree very well with the curve extrapolated from the microwave data of T. Matsuoka et al. (1996), and provide an assessment of the reliability of the experimental data of others. It is found that the existing theoretical models describe well the refractive indices in this region.