OPTICAL CONSTANTS OF AMORPHOUS AND CRYSTALLINE H2O-ICE: 2.5-22 μm (4000-455 cm–1) OPTICAL CONSTANTS OF H2O-ICE

Abstract

Using new laboratory spectra, we have calculated the real and imaginary parts of the index of refraction of amorphous and crystalline H2O-ice from 20-150 K in the wavelength range 2.5-22 μm (4000-455 cm–1) and joined these results with previous measurement from 1.25 to 2.5 μm. These optical constants improve on previous measurements by having better temperature and spectral resolution and can be used to create model spectra for comparison to spectra of solar system objects and interstellar materials. In this wavelength range, the infrared band shapes and positions of amorphous H2O-ice are strongly dependent on deposition temperature. Amorphous and crystalline H2O-ice have distinctive spectral bands at all wavelengths in this region with bands weakening and shifting to shorter wavelength in amorphous H2O-ice compared to crystalline H2O-ice. Some notable exceptions are the band near 6 μm, which is stronger in amorphous H2O-ice, and the bands near 4.5 μm and 12.5 μm, which shift to longer wavelength in amorphous H2O-ice.