Open AccessMeasurements of the 44‐ μ m band of H 2 O ice deposited on amorphous carbon and amorphous silicate substrates
Author(s) -
Maldoni Marco M.,
Robinson Garry,
Smith R. G.,
Duley W. W.,
Scott A.
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02837.x
Subject(s) - amorphous solid , silicate , amorphous ice , substrate (aquarium) , crystallization , context (archaeology) , amorphous carbon , spectral line , materials science , analytical chemistry (journal) , physics , crystallography , chemistry , geology , astronomy , organic chemistry , paleontology , oceanography , thermodynamics
We present 20–110 µm absorbance spectra of H 2 O ice, deposited on amorphous carbon and silicate substrates, obtained over the 10–140 K temperature range. The measurements have been carried out in a manner that simulates the deposition, warming and cooling of H 2 O ice mantles on interstellar and circumstellar grains. For H 2 O ice films deposited on these substrates we find (i) similar 44‐µm‐band peak wavelength temperature dependences, (ii) no bandshape differences in the respective spectra, and (iii) a structural phase transition occurring between 120 and 130 K. In comparison with published data obtained using a polyethylene substrate, the 52‐µm feature (the longitudinal optical mode) observed in our spectra is less prominent. This suggests the presence of material‐dependent substrate effects that can alter the appearance of the H 2 O far‐infrared spectrum. The crystallization temperature of H 2 O ice films deposited on our amorphous silicate substrate is significantly different from that reported by Moore et al. (1994), who found crystallization temperatures down to < 20 K for ice also deposited on an amorphous silicate substrate. This is attributed to differences in the surface structures of the respective substrates. This may indicate that, at least in the context of laboratory measurements, substrate material composition is not as significant as substrate surface structure.