Optical constants of ice from the ultraviolet to the microwave: A revised compilation

TLDR

The authors present a revised compilation of ice Ih’s spectral absorption coefficient near the melting point, superseding Warren (1984). They compiled absorption data from UV to microwave, updated mid‑IR and far‑IR measurements, extrapolated low‑temperature far‑IR data to higher temperatures, and calculated the refractive index via Kramers‑Kronig analysis, differing only in the far‑IR. The new constants show substantial reductions in blue/near‑UV, near‑IR, and microwave absorption (up to factors of 2–5), uncertain mid‑IR behavior near 9 and 20 µm, and only far‑IR refractive index differences, with tables available online.

Abstract

A compilation of the spectral absorption coefficient of ice Ih is presented for temperatures near the melting point, superseding the compilation of Warren (1984). Significant changes are made to nearly all spectral regions. The blue and near‐ultraviolet absorption is much weaker than the prior estimates, which were already very small. The near‐infrared absorption coefficient differs by as much as a factor of 2 from the prior compilation at some wavelengths. The midinfrared absorption coefficient is rather uncertain in the weakly absorbing regions near 9 and 20 μ m. New far‐infrared measurements at low temperatures are extrapolated to higher temperatures, which shifts the peak positions. New microwave measurements find absorption much weaker than previously reported, by factors of 2–5. The real part of the index of refraction is computed using Kramers‐Kronig analysis; it differs from the prior compilation only in the far infrared. Tables of the revised optical constants are available on a website.