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Experiments involving the irradiation of water contained within magnesium hydroxide and alumina nanoparticle sludges were conducted and culminated in observations of an increased yield of molecular hydrogen when compared to the yield from the irradiation of bulk water. We show that there is a relationship linking this increased yield to the direct nanoscale ionization mechanism in the nanoparticles, indicating that electron emission from the nanoparticles drives new radiative pathways in the water. Because the chemical changes in these sludges are introduced by irradiation only, we have a genuinely unstirred system. This feature allows us to determine the diffusivity of the dissolved gas. Using the measured gas production rate, we have developed a method for modelling when hydrogen bubble formation will occur within the nanoparticle sludges. This model facilitates the determination of a consistent radiolytic consumption rate coinciding with the observations of bubble formation. Thus, we demonstrate a nanoscale radiation effect directly influencing the formation of molecular hydrogen. [ABSTRACT FROM AUTHOR]

The application of pressure to materials can reveal unexpected chemistry. Under compression, noble gases form stoichiometric van der Waals (vdW) compounds with closed-shell molecules such as hydrogen, leading to a variety of unusual structures. We have synthesised Kr(H2)4 for the first time in a diamond-anvil high-pressure cell at pressures≥5.3 GPa and characterised its structural and vibrational properties to above 50 GPa. The structure of Kr(H2)4, as solved by single-crystal synchrotron X-ray diffraction, is face-centred cubic (fcc) with krypton atoms forming isolated octahedra at fcc sites. Rotationally disordered H2 molecules occupy four different, interstitial sites, consistent with the observation of four Raman activeH2 vibrons. The discovery of Kr(H2)4 expands the range of pressure-stabilised, hydrogen-rich vdW solids, and, in comparison with the two known rare-gas-H2 compounds, Xe(H2)8 and Ar(H2)2, reveals an increasing change in hydrogen molecular packing with increasing rare gas atomic number. [ABSTRACT FROM AUTHOR]

Absolute measurements of the radiolytic yield of Fe3+ in a ferrous sulphate dosimeter formulation (6 mM Fe2+), with a 20 keV x-ray monoenergetic beam, are reported. Dose-rate suppression of the radiolytic yield was observed at dose rates lower than and different in nature to those previously reported with x-rays. We present evidence that this effect is most likely to be due to recombination of free radicals radiolytically produced from water. The method used to make these measurements is also new and it provides radiolytic yields which are directly traceable to the SI standards system. The data presented provides new and exacting tests of radiation chemistry codes.