Probing icy surfaces with the dangling-OH-mode absorption: Large ice clusters and microporous amorphous ice

Abstract

Infrared absorption bands that have previously been assigned to vibrations of the dangling bonds (db) of water molecules at the surfaces of crystalline ice clusters and the micropores of amorphous ice have been investigated to determine their usefulness in probing molecular-level events at icy surfaces. This study has established that the db bands are sensitive to adsorption of gases at the cluster or micropore surfaces, and that reversible adsorption/desorption at the db sites is readily monitored spectroscopically. Consequently, energetics for the interactions with adsorbents such as H2 and N2 are potentially measurable. It has also been demonstrated, for both clusters and the micropores, that surface HOD molecules give unique db band positions, and that the intensities of the db bands are indicative of a strong preference of the surface HOD molecules to engage in deuterium bonding to the subsurface molecules. The unique positions of the HOD db bands also signals a potential for using isotopic-exchange data to monitor point-defect activity at icy surfaces.

Thermal Evolution of Acetic Acid Nanodeposits over 123−180 K on Noncrystalline Ice and Polycrystalline Ice Studied by FTIR Reflection−Absorption Spectroscopy: Hydrogen-bonding Interactions in Acetic Acid and between Acetic Acid and Ice

“…For example, the study of the adsorption of hydrogen and nitrogen on NCI by Rowland et al has revealed red shifts of 10 cm -1 in these dangling-bond features for doubly coordinated and triply coordinated adsorption sites. 13 In the case when strong H-bonding is involved in the adsorption of a guest species, the red shift in the OH dangling bond is expected to increase. 12 The weak OH dangling-bond feature for a guest species (e.g., acetone) upon adsorption on ice could then be obscured by the much stronger OH stretch feature of the bulk if the magnitude of the red-shift happens to be large.…”

Near-infrared laboratory spectra of H2O trapped in N2, CH4, and CO: hints for trans-Neptunian objects' observations

“…Two small features are also present on the wing of the O-H stretching modes band, whose peak positions are at 3720 and 3697 cm −1 (2.69 and 2.70 µm, respectively). These weak bands come from O-H dangling bonds in the micropores of the porous structure of amorphous water ice (e.g., Rowland et al 1991;Palumbo 2006). By warming up amorphous water-ice, a more ordered (i.e.…”

“…If this sample is warmed up, at about 30 K, N 2 diffusion in the porous structure of solid water takes place. The diffusion is proven by the shift of the O-H dangling bonds features from 3697 to 3672 cm −1 and from 3720 to 3690 cm −1 (Rowland et al 1991;Palumbo & Strazzulla 2003). Furthermore, Palumbo & Strazzulla (2003) have shown that a band at 5300 cm −1 appears after diffusion of N 2 in porous amorphous solid water.…”

“…Figure 4 shows, in two different spectral regions, the spectrum of N 2 condensed at 15 K on water ice previously deposited at 80 K and cooled down to 15 K. We can see the broad absorption band at about 5000 cm −1 due to polymeric water. Moreover, as discussed by Rowland et al (1991), the profile of the O-H dangling bond depends on the temperature of the sample; in particular, the spectrum of water ice cooled from 80 K to 15 K shows only the O-H dangling bond band at 3695 cm −1 , so we can use it, together with the 5300 cm −1 band, to investigate if N 2 diffusion is occurring. After N 2 deposition at 15 K, we can see a change in the continuum trend around 5000 cm −1 because of the increasing thickness of the deposited ice.…”

“…In both cases the obtained samples were afterwards warmed (26-32 K) to induce the diffusion of N 2 into H 2 O. The diffusion was probed in both experiments by means of the narrow feature arising around 5300 cm −1 and, in the case of water ice deposited at 80 K, also by means of the shift of the O-H dangling bond' peak position (Rowland et al 1991;Palumbo & Strazzulla 2003). Figure 4 shows, in two different spectral regions, the spectrum of N 2 condensed at 15 K on water ice previously deposited at 80 K and cooled down to 15 K. We can see the broad absorption band at about 5000 cm −1 due to polymeric water.…”