Boehmite (γ-AlOOH) and gibbsite (α-Al(OH) 3 ) are important archetype (oxy)hydroxides of aluminum in nature that also play diverse roles across a plethora of industrial applications. Developing the ability to understand and predict the properties and characteristics of these materials, on the basis of their natural growth or synthesis pathways, is an important 1 fundamental science enterprise with wide ranging impacts. The present study describes bulk and surface characteristics of these novel materials in comprehensive detail, using a collectively-sophisticated set of experimental capabilities, including a range of conventional laboratory solids analyses and national user facility analyses such as synchrotron X-ray absorption and scattering spectroscopies, as well as small angle neutron scattering. Their thermal stability is investigated using in situ temperature-dependent Raman spectroscopy. These pure and effectively defect-free materials are ideal for synthesis of advanced alumina products.

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The solar wind has been implicated as a source of water on airless bodies such as the Moon, asteroids, and possibly Mercury, yet a kinetic and mechanistic chemical model consistent with present-day observational data is still lacking. Utilizing available data sets on temperature-driven water formation and desorption from metal oxides (e.g., SiO 2 , TiO 2 , and Al 2 O 3 ) with surface hydroxyl defects (─OH) and experimental data from a lunar mare regolith Apollo sample (10084), the 2.8-μm optical signal on the Moon is modeled. Specifically, the presence and persistence of this band result from the balance of formation and loss mechanisms associated with solar wind production and thermal transformation of hydroxyls on and within the regolith. This cycle involves formation and release of molecular water via recombinative desorption of the chemically bound ─OH. Though this mechanism forms gas-phase H 2 O on the sunlit side, photodissociation and dissociative adsorption lead to rehydroxylation and very limited exospheric water over a lunation.Plain Language Summary The idea that water exists on the Moon has been around for many years, and its presence would provide a useful resource for human exploration. Lunar water is often observed by examining the 2.8-3 micron optical absorption feature seen in the reflecting sunlight. This feature is mainly associated with bound ─OH groups made from solar wind implantation and/or from molecular water dissociating upon adsorption onto the regolith. Molecular water can form when the Moon's surface reaches 50 K above room temperature. In this process, neighboring ─OH groups combine and react producing molecular water. This has been documented to occur at these relatively low temperatures for some metal oxides that are known constituents of the lunar regolith. The water will then leave following a ballistic trajectory and either molecularly adsorb or dissociate. We have modeled this process and show that the recent observations of the Moon's water may be mostly related to the presence of ─OH and only a small amount of exospheric water. This process can also happen on asteroids and Mercury or any other surface that is bombarded by the solar wind and can heat up above 350 K.

Elastic scattering of 5-30 eV electrons within the B-DNA 5'-CCGGCGCCGG-3' and A-DNA 5'-CGCGAATTCGCG-3' DNA sequences is calculated using the separable representation of a free-space electron propagator and a curved wave multiple scattering formalism. The disorder brought about by the surrounding water and helical base stacking leads to a featureless amplitude buildup of elastically scattered electrons on the sugar and phosphate groups for all energies between 5 and 30 eV. However, some constructive interference features arising from diffraction are revealed when examining the structural waters within the major groove. These appear at 5-10, 12-18, and 22-28 eV for the B-DNA target and at 7-11, 12-18, and 18-25 eV for the A-DNA target. Although the diffraction depends on the base-pair sequence, the energy dependent elastic scattering features are primarily associated with the structural water molecules localized within 8-10 A spheres surrounding the bases and/or the sugar-phosphate backbone. The electron density buildup occurs in energy regimes associated with dissociative electron attachment resonances, direct electronic excitation, and dissociative ionization. Since diffraction intensity can be localized on structural water, compound H2O:DNA states may contribute to energy dependent low-energy electron induced single and double strand breaks.

[1] Interactions of molecular water with two lunar regolith surrogates (micronized JSC-1A and albite) were examined using temperature program desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy. TPD revealed water desorption during initial heating to 750 K under ultrahigh vacuum and diffuse reflectance infrared Fourier transform spectroscopy indicated possible water formation via recombinative desorption of native hydroxyls above 425 AE 25 K. Dissociative chemisorption of water (i.e., formation of surface hydroxyl sites) was not observed on laboratory time scales after controlled dosing of samples (initially heated above 750 K) with 0.2-500 L exposures of water. However, preheated samples of both types of surrogates were found to have a distribution of molecular water chemisorption sites, with albite having at least twice as many as the JSC-1A samples by mass. A fit to the TPD data yields a distribution function of desorption activation energies ranging from~0.45 to 1.2 eV. Using the fitted distribution function as an initial condition, the TPD process was simulated on the time scale of a lunation.