English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

CO is one of the most abundant ice components on interstellar dust grains.When it is mixed with amorphous solid water (ASW) or located on its surface, anabsorption band of CO at 2152 cm$^{-1}$ is always present in laboratorymeasurements. This spectral feature is attributed to the interaction of CO withdangling-OH bonds (dOH) in ASW. However, this band is absent in observationalspectra of interstellar ices. This raises the question whether CO forms arelatively pure layer on top of ASW or is in close contact with ASW, but notvia dangling bonds. We aim to determine whether the incorporation of NH$_3$ orCO$_2$ into ASW blocks the dOH and therefore reduces the 2152 cm$^{-1}$ band.We performed laboratory experiments to simulate the layered structure of theice mantle, that is, we grew CO ice on top of 1) pure ASW, 2)NH$_3$:H$_2$O=10:100 mixed ice, and 3) CO$_2$:H$_2$O=20:100 mixed ice. Infraredspectra were measured to quantify the strength of the 2152 cm$^{-1}$ band. Inaddition, a second set of experiments were performed to determine how theincorporation of NH$_3$ into ASW affects the dOH band. We found that annealingthe ice reduces the 2152 cm$^{-1}$ band and that NH$_3$ blocks the dOH on ASWsurface and therefore reduces the 2152 cm$^{-1}$ band more effectively thanCO$_2$. We suggest that this difference between NH$_3$ and CO$_2$ can beascribed to the polarity of the guest molecule (NH$_3$ is a polar species,whereas CO$_2$ is apolar). The polarity implies that the formation of an H-bondbetween the N atom of ammonia and the dOH is a barrier-less reaction. We alsodetermined the pore surface area of the ice mixtures as a function of theannealing temperature, and found that the nondetection of 2152 cm$^{-1}$ banddoes not necessarily exclude the possibility of a porous ice mantle.

Ammonia, carbon dioxide and the non-detection of the 2152 cm$^{-1}$ CO band