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The formation of molecules in and on amorphous solid water (ASW) as it occurs in interstellar space releases appreciable amounts of energy that need to be dissipated to the environment. Here, energy transfer between CO2 formed within and on the surface of amorphous solid water (ASW) and the surrounding water is studied. Following CO(1Σ+) + O(1D) recombination the average translational and internal energy of the water molecules increases on the ∼10 ps time scale by 15–25% depending on whether the reaction takes place on the surface or in an internal cavity of ASW. Due to tight coupling between CO2 and the surrounding water molecules the internal energy exhibits a peak at early times which is present for recombination on the surface but absent for the process inside ASW. Energy transfer to the water molecules is characterized by a rapid ∼10 ps and a considerably slower ∼1 ns component. Within 50 ps a mostly uniform temperature increase of the ASW across the entire surface is found. The results suggest that energy transfer between a molecule formed on and within ASW is efficient and helps to stabilize the reaction products generated.

Electron beam lithography (EBL) on amorphous solid water (ASW), termed as ice lithography (IL), has demonstrated promising capability in pattern transfer with unique advantages such as reduced proximity effect. So far, ice lithography for binary patterning has been proved a great success, however, application for three-dimensional (3D) profiling in nanoscale has still not been addressed to the best of our knowledge. This paper reports, for the first time, our progress in simulating study of three-dimensional ice lithography on ASW for linear blazed gratings, aiming to overcome the difficulty in replicating high quality blazed gratings with high diffraction efficiency. Systematic simulation of grayscale ice lithography for 3-D blazed grating templates with desired surface quality as the task was carried out, using Monte Carlo algorithm based on the measured contrast curves of ASW. For comparison, grayscale electron beam lithography on PMMA was also performed. The resultant profiles of blazed wavelengths around 1550 nm by grayscale IL show less flaws and higher diffraction efficiencies than by EBL. The successful simulation of 3D grayscale IL provides us with instructive guide for the fabrication of 3D nanostructures as a whole through the grayscale ice lithography on ASW. [Display omitted] • Amorphous solid water acts as a unique positive-tone electron resist for grayscale ice lithography (IL). • Systematic simulation of grayscale ice lithography for 3D blazed grating templates was carried out by Monte Carlo algorithm. • The simulated profiles by grayscale IL show less flaws and higher diffraction efficiencies than by traditional EBL. • Grayscale ice lithography can be used to fabricate the 3D nanostructures more flexibly. [ABSTRACT FROM AUTHOR]

Physico-chemical instability is commonly associated with the amorphous state, and the understanding of instability mechanisms (e.g. the glass transition) involved is essential in designing pharmaceutical products. The glass transition of bulk water might occur at 210 K [Oguni et al., J. Phys. Chem. B115 (2011) 14023] but it was recently proposed the glass transition of water could happen around 121 K [C. R. Hill et al., Phys. Rev. Lett.116 (2016) 215501]. Note that molecular self-inclusions in a glassy water show relaxation features that are characteristically different from those observed in thermodynamically stable, crystalline solids with inclusions. Here we point out some doubtful results and calculations in Hill et al.'s work [C. R. Hill et al., Phys. Rev. Lett.116 (2016) 215501] which was based on the small-angle neutron scattering (SANS) measurements. We also made some remarks about the possible mistakes in their previous works [C. Mitterdorfer, Phys. Chem. Chem. Phys.16 (2014) 16013] considering the calculation of the specific surface area. The latter is crucial to the doubtful fixing of the glass transition temperature in Hill et al.'s work [C. R. Hill et al., Phys. Rev. Lett.116 (2016) 215501]. [ABSTRACT FROM AUTHOR]

Clathrate hydrates (CHs) are ubiquitous in earth under highpressure conditions, but their existence in the interstellar medium (ISM) remains unknown. Here, we report experimental observations of the formation of methane and carbon dioxide hydrates in an environment analogous to ISM. Thermal treatment of solid methane and carbon dioxide-water mixture in ultrahigh vacuum of the order of 10-10 mbar for extended periods led to the formation of CHs at 30 and 10 K, respectively. High molecular mobility and H bonding play important roles in the entrapment of gases in the in situ formed 512 CH cages. This finding implies that CHs can exist in extreme low-pressure environments present in the ISM. These hydrates in ISM, subjected to various chemical processes, may act as sources for relevant prebiotic molecules. [ABSTRACT FROM AUTHOR]

To investigate the influence of foreign gas inclusion on the crystallization of ice, we studied the low-temperature (74 <  T  < 160 K) vacuum deposition of water molecules mixed with Kr or CH 4 in a wide range of H 2 O/gas mixing ratios (0.004 <  R  < 4) by means of in-situ X-ray diffraction. When H 2 O vapor containing either Kr or CH 4 was condensed onto a cold substrate, ice Ih crystals were found to grow below 130 K in a film of amorphous solid water (ASW), whereas pure H 2 O gas formed only ASW below 135 K. Small to moderate concentrations ( R  > 0.2) of Kr and CH 4 enhance the formation of ice Ih and increase the crystal size, while at high foreign gas contents ( R  ⩽ 0.2) that may develop Kr or CH 4 crystals below 92 K, the crystal size and relative amount of ice decrease strongly. The maximum ice Ih crystal size in the order of 200 nm was observed with either Kr or CH 4 at 92 K for R = 0.2. We propose that Kr and CH 4 induce the crystallization of ice by acting as a surfactant. [ABSTRACT FROM AUTHOR]

The crystallization kinetics of nanoscale amorphous solid water (ASW) films are investigated using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). TPD measurements are used to probe surface crystallization and RAIRS measurements are used to probe bulk crystallization. Isothermal TPD results show that surface crystallization is independent of the film thickness (from 100 to 1000 ML). Conversely, the RAIRS measurements show that the bulk crystallization time increases linearly with increasing film thickness. These results suggest that nucleation and crystallization begin at the ASW/vacuum interface and then the crystallization growth front propagates linearly into the bulk. This mechanism was confirmed by selective placement of an isotopic layer (5% D 2 O in H 2 O) at various positions in an ASW (H 2 O) film. In this case, the closer the isotopic layer was to the vacuum interface, the earlier the isotopic layer crystallized. These experiments provide direct evidence to confirm that ASW crystallization in vacuum proceeds by a “top-down” crystallization mechanism. [ABSTRACT FROM AUTHOR]

Interactions of molecular additives with amorphous solid water have been investigated using time-of-flight secondary ion mass spectrometry and temperature programmed desorption. The crystallization temperature of water on a clean graphite substrate decreases from the bulk value of 160 K to 150 K when water deposition temperature increases from 20 K to 100 K. This phenomenon is induced by the formation of a specifically oriented water layer at the interface, as evidenced by that a submonolayer of n -hexane adspecies on graphite quenches this behavior. Thermal desorption spectra of additives reflect their hydration forms. The n -hexane molecules are trapped in the interior of a porous water film via hydrophobic hydration and released explosively during crystallization. The thermal desorption spectra of methanol resemble those of water from multilayer films because methanol can enter the hydrogen-bond network of water via hydrophilic hydration. The hydration of formaldehyde is hydrophobic in nature despite the presence of the polar carbonyl group. Features of both hydrophilic and hydrophobic hydrations are identifiable in acetone–water interactions; the branching ratio depends on the water preparation method and substrate. [ABSTRACT FROM AUTHOR]

Molecular clouds (MCs) in space are the birthplace of various molecular species. Chemical reactions occurring on the cryogenic surfaces of cosmic icy dust grains have been considered to play important roles in the formation of these species. Radical reactions are crucial because they often have low barriers and thus proceed even at low temperatures such as ∼10 K. Since the 2000s, laboratory experiments conducted under low-temperature, high-vacuum conditions that mimic MC environments have revealed the elementary physicochemical processes on icy dust grains. In this review, experiments conducted by our group in this context are explored, with a focus on radical reactions on the surface of icy dust analogues, leading to the formation of astronomically abundant molecules such as H 2 , H 2 O, H 2 CO, and CH 3 OH and deuterium fractionation processes. The development of highly sensitive, non-destructive methods for detecting adsorbates and their utilization for clarifying the behavior of free radicals on ice, which contribute to the formation of complex organic molecules, are also described.

Ice clouds form in the summer high latitude mesopause region, which is the coldest part of the Earth's atmosphere. At these very low temperatures (<150 K) ice can exist in metastable forms, but the nature of these ices remains poorly understood. In this paper we show that ice which is grown at mesospherically relevant temperatures does not have a structure corresponding to the well-known hexagonal form or the metastable cubic form. Instead, the ice which forms under mesospheric conditions is a material in which cubic and hexagonal sequences of ice are randomly arranged to produce stacking disordered ice (ice I sd ). The structure of this ice is in the trigonal crystal system, rather than the cubic or hexagonal systems, and is expected to produce crystals with aspect ratios consistent with lidar observations. [ABSTRACT FROM AUTHOR]

Au-Cu and Pd-Cu bimetallic model catalysts were prepared on native SiO/Si(100) substrate under ultra high vacuum (UHV) by employing buffer layer assisted growth procedure with amorphous solid water as the buffer material. The effect of the bimetallic nanoclusters (NCs) surface composition and morphology on their chemical reactivity has been studied with acetylene decomposition and conversion to ethylene and benzene as the chemical probe. It was found that among the Au-Cu NCs compositions, AuCu NCs revealed outstanding catalytic selectivity towards ethylene formation. These NCs were further characterized by employing TEM, XPS and HAADF-STEM coupled EDX analysis. With CO molecule as a probe, CO temperature programmed desorption has been used to investigate the distribution of gold on the top-most surface of the supported clusters. Surface segregation at high relative elemental fraction of gold leads to a decreased activity of the Au-Cu NCs towards ethylene formation. In contrast to the Au-Cu NCs, the Pd-Cu bimetallic system reveals reduced sensitivity to the relative elemental composition with respect to selectivity of the acetylene transformation toward ethylene formation. On the other hand, remarkable activity towards benzene formation has been observed at elemental composition of CuPd, at comparable rates to those for ethylene formation on clean Pd NCs. [ABSTRACT FROM AUTHOR]

Abstract: The photoprocesses of water ice play an important role in regions of interstellar space, such as interstellar clouds and outer solar systems. Vacuum-ultraviolet absorption of water ice leads to dissociation of water molecules, and allows subsequent reactions of photoproducts on/in ice. There have been many laboratory studies that identify photoproducts and estimate product yields, reaction mechanisms and energy partitioning in the reaction products. Among them, the experimental approaches aimed at understanding the photoprocesses on the water ice surface can give new insight into the chemical reaction network in interstellar space. In this review, we focus on photochemical processes of water ice relevant to surface astrochemistry following vacuum-ultraviolet photolysis of water ice at a low temperature from a surface reaction dynamics’ point of view. [Copyright &y& Elsevier]

Abstract: Water ice is the major solid component in a variety of astrophysical environments, e.g., cold and dense molecular clouds. Photodesorption plays a dominant role in consuming ice in such cold regions. In this study, photodesorption of vibrationally ground-state H2O(v =0) from amorphous solid water has been investigated at 157nm. Using a resonance-enhanced multiphoton ionization technique, the translational and rotational energy distributions of photodesorbed H2O(v =0) were measured, i.e., Boltzmann distributions at 1800 and 300K, respectively. These energies are in good accordance with those predicted by classical molecular calculations for water photodesorption due to a kick-out mechanism following absorption of a single photon; hot H atom released by photodissociation of H2O in ice transfers enough momentum to another H2O molecule to kick it off the surface. Desorption of D2O(v =0) following 193nm photoirradiation of a D2O/H2S mixed ice was investigated to provide further direct evidence for the operation of a kick-out mechanism. The other desorption mechanisms were also discussed in the context of possible photodesorption of vibrationally excited H2O. [Copyright &y& Elsevier]

Abstract: Condensed water particles are known to exist in the high latitude upper mesosphere during the summer months. However, the mechanism or mechanisms through which they nucleate remains uncertain. It is postulated here that particles of amorphous solid water (ASW, condensed water with a non-crystalline structure) may nucleate homogeneously in the summer mesosphere. Using classical nucleation theory and a one-dimensional model, it is shown that more than 105 cm−3 amorphous solid water particles can nucleate homogeneously under mesopause conditions. Furthermore, it is shown that homogeneous nucleation competes with heterogeneous nucleation on meteoric smoke particles when the cooling rate is >0.5K/h. The homogeneous nucleation of amorphous solid water could provide an explanation for the high density of ice particles (many thousands per cm3) thought to be required for electron depletions in the upper mesosphere. A parameterisation for homogeneous nucleation is presented which can be used in other mesospheric cloud models. [Copyright &y& Elsevier]

Abstract: The phase conversion of amorphous solid water (ASW) to crystalline ice (CI) has been investigated in the very thin (10 monolayers) film regime on a Ru(001) surface. We analyze the converted CI fraction with the Avrami model, and recognize that one-dimensional CI growth occurs, which can be contrasted to the three-dimensional CI growth generally established in the thick ( monolayers) film regime. We evaluate activation energy for the ASW crystallization to be about 1.0eV. We suggest that the ASW crystallization is not influenced by the substrate even near the substrate–ice interface. [Copyright &y& Elsevier]

Abstract: Chemical reactions on the surface of cosmic ice dust play an important role in chemical evolution in space. Among the many kinds of molecules observed, the abundances of some major species such as hydrogen molecules cannot be explained by gas-phase synthesis; therefore, surface reactions on cosmic dust are considered for the synthesis of such molecules. Experimental research on surface reactions relevant to cosmic ice dust has been conducted since the late 1980s. Early experiments were rather qualitative, and so the details of reactions were not clear. In the last decade, many scientists from various fields including surface science have been motivated to extend the knowledge in this area of research, and have performed sophisticated experiments regarding surface reactions on cosmic ice dust. The aim of this article is to review the recent progress in surface astrochemistry. In particular, focus is made on experiments concerning the synthesis of abundant molecules such as H2, H2O, CO2, H2CO and CH3OH on ice surfaces at very low temperatures. [Copyright &y& Elsevier]

Abstract: Electron emission spectra from thin metal foils with thin layers of water frozen on them (amorphous solid water) after fast proton impact have been measured and have been simulated in liquid water using the event-by-event track structure code PARTRAC. The electron transport model of PARTRAC has been extended to simulate electron transport down to 1eV by including low-energy phonon, vibrational and electronic excitations as measured by Michaud et al. [Michaud, M., Wen, A., Sanche, L., 2003. Cross sections for low-energy (1–100eV) electron elastic and inelastic scattering in amorphous ice. Radiat. Res. 159, 3–22] for amorphous ice. Simulated liquid water yields follow in general the amorphous solid water measurements at higher energies, but overestimate them significantly at energies below 50eV. [Copyright &y& Elsevier]

Abstract: Solid water films are used to create a wide range of nanostructures through buffer-layer-assisted growth. Metal atoms vapor-deposited onto solid water films form clusters that aggregate as the film is heated. The aggregation process is driven by the dewetting, islanding, and sublimation of the ice films. The sizes, shapes, and densities of the resulting nanostructures are determined by the formation of ice islands whose sizes and densities are controlled by the thickness of the ice film. [Copyright &y& Elsevier]

Abstract: The adsorption and photochemistry of bromoform multilayers on and in amorphous solid water (ASW) are studied using reflection absorption infrared spectroscopy (RAIRS), temperature-programmed desorption (TPD), and time-of-flight (TOF) techniques. Regardless of the initial exposure, bromoform resides on top of the ASW layer. No migration of bromoform molecules into the ASW film is observed for adsorption on top of the water layer. UV irradiation at a wavelength of 266nm results in significant desorption of photochemical fragments, reaction of photochemical products on the surface and light-induced molecular reorganization of the remaining CHBr3, which is apparent from a comparison of pre- and post-irradiation TPD experiments. The ice-mediated C–C (C2H2Br2) and C–O (CHBrO) photoproducts desorb from both the ASW surface and the Pt surface. The photoproduct C2H2Br4 is formed exclusively from multilayers of CHBr3 and desorbs only from the Pt surface. [Copyright &y& Elsevier]

Summary Amorphous solid (vitreous) water can be obtained by a number of methods, including quick freezing of a very small volume of pure water, low pressure condensation of water vapour on a cold substrate or transformation of hexagonal ice (the ice which is naturally formed) under very high pressure at liquid nitrogen temperature. Larger volumes can be vitrified if cryoprotectant is added or when samples are frozen under high pressure. We show that a sample of 17.5% dextran solution or mouse brain tissue, respectively, frozen under high pressure (200 MPa) into cubic or hexagonal ice can be transformed into vitreous water by the very process of cryosectioning. The vitreous sections obtained by this procedure differ from cryosections obtained from vitreous samples by the irregular aspect of the sections and by small but significant differences in the electron diffraction patterns. For the growing community of cryo-ultramicrotomists it is important to know that vitrification can occur at the knife edge. A vitreous sample is considered to show the best possible structural preservation. The sort of vitrification described here, however, can lead to bad structural preservation and is therefore considered to be a pitfall. Furthermore, we compare these sections with other forms of amorphous solid water and find it similar to high density amorphous water produced at very high pressures (about 1 GPa) from hexagonal ice and annealed close to its transformation temperature at 117 K. [ABSTRACT FROM AUTHOR]

The formation of molecules in and on amorphous solid water (ASW) as it occurs in interstellar space releases appreciable amounts of energy that need to be dissipated to the environment. Here, energy transfer between CO 2 formed within and on the surface of amorphous solid water (ASW) and the surrounding water is studied. Following CO( 1 Σ + ) + O( 1 D) recombination the average translational and internal energy of the water molecules increases on the ∼ 10 ps time scale by 15-25% depending on whether the reaction takes place on the surface or in an internal cavity of ASW. Due to tight coupling between CO 2 and the surrounding water molecules the internal energy exhibits a peak at early times which is present for recombination on the surface but absent for the process inside ASW. Energy transfer to the water molecules is characterized by a rapid ∼ 10 ps and a considerably slower ∼ 1 ns component. Within 50 ps a mostly uniform temperature increase of the ASW across the entire surface is found. The results suggest that energy transfer between a molecule formed on and within ASW is efficient and helps to stabilize the reaction products generated., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Upadhyay and Meuwly.)

• Amorphous solid water acts as a unique positive-tone electron resist. • Ice thickness removed by electron irradiation has a strong linear dependence on applied electron doses. • Ice formed on hydrophilic surfaces resists more irradiation than on the hydrophobic. • Ice nanodots and "micro-snowflakes" are attained after e-beam patterning. • Ice can be used to regulate lithographic properties of conventional electron resists. Amorphous solid water (ASW) formed by vapor deposition at cryogenic temperatures acts as an emerging competitive electron resist with virtues like direct patterning and easy removal. In this work, we systematically study the properties of the ASW resist and assess its performance for lithographic applications. Dose curves show that ASW has a low contrast of ~1.6 and it is barely affected by the incident electron energy. Ice elimination is almost linear to applied electron doses. The calculated rate is around 30 μm3/μC at 10 kV, implying approximately seven electrons remove one water molecule in this case. The minimum linewidth of 12 nm is obtained on a 120-nm-thick ASW film and refined nanostructures such as ice nanodots and "micro-snowflakes" are also presented. Finally, we perform e-beam exposure on a bilayer configuration of ASW/PMMA resist and provide an alternative way to regulate lithographic properties of conventional electron resists. [ABSTRACT FROM AUTHOR]

The diffusion of hydronium (H3O(+)) and hydroxide (OH(-)) ions is one of the most intriguing topics in aqueous chemistry. It is considered that these ions in aqueous solutions move via sequential proton transfer events, known as the Grotthuss mechanisms. Here, we present an experimental study of the diffusion and H/D exchange of hydronium and hydroxide ions in amorphous solid water (ASW) at 140-180 K by using low-energy sputtering (LES) and temperature-programmed desorption (TPD) measurements. The study shows that the two species transport in ASW via fundamentally different molecular mechanisms. Whereas hydronium ions migrate via efficient proton transfer, hydroxide ions move via Brownian molecular diffusion without proton transfer. The molecular hydroxide diffusion in ASW is in stark contrast to the current view of the hydroxide diffusion mechanism in aqueous solution, which involves proton transfer.