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The temperature dependent dehydrogenation of naphthalene on Ni(111) has been investigated using vibrational sum-frequency generation spectroscopy, X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory with the aim of discerning the reaction mechanism and the intermediates on the surface. At 110 K, multiple layers of naphthalene adsorb on Ni(111); the first layer is a flat lying chemisorbed monolayer, whereas the next layer(s) consist of physisorbed naphthalene. The aromaticity of the carbon rings in the first layer is reduced due to bonding to the surface Ni-atoms. Heating at 200 K causes desorption of the multilayers. At 360 K, the chemisorbed naphthalene monolayer starts dehydrogenating and the geometry of the molecules changes as the dehydrogenated carbon atoms coordinate to the nickel surface; thus, the molecule tilts with respect to the surface, recovering some of its original aromaticity. This effect peaks at 400 K and coincides with hydrogen desorption. Increasing the temperature leads to further dehydrogenation and production of H2 gas, as well as the formation of carbidic and graphitic surface carbon. [ABSTRACT FROM AUTHOR]

Pulsed-laser ablation of an aluminum bulk sample was performed both in water and air with a Q-switched Nd:YAG 1,064-nm laser over a range of high-output energies from 100 to 500 mJ. The effect of laser drilling in terms of produced crater volumes as a function of water-layer thickness was studied. The water-layer thickness was varied from 1 to 20 mm. In a special case, water droplets were added to the ablation region of the dry target in order to support ablation. Water-layer thickness in that case was estimated to be 0.5 mm. A comparison of the results obtained in air and underwater was performed. It is found that the aluminum target may be drilled more efficiently under the confinement of water compared to drilling in air environment. Further drilling efficiency can be achieved by varying the thickness of water. The optimized water thickness under the conditions of our experiment was found to be 3 mm. In that case, a 28-fold increase in crater volume and 18-fold increase in crater depth was achieved as compared to ablation in air. In underwater ablation, the formation of irregular surface structures of re-deposited material around the crater (rim) is avoided and the crater surface is smoother. In an air environment, the drilling is suppressed due to an immediate re-solidification and re-deposition of ablated material. This leads to a better characteristics of craters obtained underwater in terms of roughness, shape, volumes, and reproducibility. [ABSTRACT FROM AUTHOR]