SIMBAD references

Data on the sub-millimetre opacity of cold dust components such as H₂O ice and others are so far rare in the literature, in particular for solid-state structures different from bulk crystals. In this paper, we present measurements of the extinction coefficient for high-density and low-density amorphous H₂O ice, as well as for micron-sized water-ice particles in dense agglomerates for the wavelength range from 300 µm to roughly 1 mm. The temperature range is mainly 80 K up to 120 K, where amorphous phases remain stable, but effects of warming to higher temperature are studied as well. We find that the opacity of high-density amorphous ice is 5-20 times higher than that of bulk crystalline (Ih) ice, depending on the wavelength, while for low-density ice it is about three times lower than for high-density ice. This result is consistent with literature data measured at 11 K temperature at 500 µm wavelength, but indicates a significant temperature dependence at longer wavelengths. Even at 80-120 K, the values are lower than certain extrapolated data that are often used in astrophysical modelling. For the micron-sized ice particles, which consist of about 90 per cent crystalline and 10 per cent amorphous ice we find, after correction with an effective-medium approach, extinction coefficients close to, but systematically higher than that of crystalline hexagonal ice. The extinction can be repeatedly enhanced to about the values characteristic of low-density amorphous ice by applying pressure of 0.5 GPa and restored by thermal annealing.