A revised rotation-vibration line list for the combined hydrogen cyanide (HCN) / hydrogen isocyanide (HNC) system is presented. The line list uses ab initio transition intensities calculated previously (Harris et al., ApJ, 2002, 578, 657) and extensive datasets of recently measured experimental energy levels (Mellau, J. Chem. Phys. and J. Mol. Spectrosc. 2010. The resulting line list has significantly more accurate wavelengths than previous ones for these systems. An improved value for the separation between HCN and HNC is adopted leading to an approximately 25 % lower predicted thermal population of HNC as a function of temperature in the key 2000 to 3000 K region. Temperature-dependent partition functions and equilibrium constants are presented. The line lists are validated by comparison with laboratory spectra and are presented in full as supplementary data to the article and at www.exomol.com.

It is shown that both the materials and the pressure gaps can be bridged for ruthenium in heterogeneous oxidation catalysis using the oxidation of carbon monoxide as a model reaction. Polycrystalline catalysts, such as supported Ru catalysts and micrometer-sized Ru powder, were compared to single-crystalline ultrathin RuO 2 films serving as model catalysts. The microscopic reaction steps on RuO 2 were identified by a combined experimental and theoretical approach applying density functional theory. Steady-state CO oxidation and transient kinetic experiments such as temperature-programmed desorption were performed with polycrystalline catalysts and single-crystal surfaces and analyzed on the basis of a microkinetic model. Infrared spectroscopy turned out to be a valuable tool allowing us to identify adsorption sites and adsorbed species under reaction conditions both for practical catalysts and for the model catalyst over a wide temperature and pressure range. The close interplay of the experimental and theoretical surface science approach with the kinetic and spectroscopic research on catalysts applied in plug-flow reactors provides a synergistic strategy for improving the performance of Ru-based catalysts. The most active and stable state was identified with an ultrathin RuO 2 shell coating a metallic Ru core. The microscopic processes causing the structural deactivation of Ru-based catalysts while oxidizing CO have been identified.

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In situ reflection-absorption infrared spectroscopy (RAIRS) experiments identify the most abundant surface species during the CO oxidation on RuO 2 (110) in a wide pressure range from 10 -7 mbar to 10 -3 mbar. Under reaction conditions with highest catalytic activity most of the undercoordinated (bridging) surface O atoms of the RuO 2 (110) surface are shown to be replaced by bridging CO molecules, thereby modifying the operating catalyst. The observed replacement of bridging O by bridging CO contradicts recently published ab initio kinetic Monte Carlo (k-MC) simulations on the same catalytic system. The C-O stretching frequency depends not only on the adsorption site but also on the local adsorption environment on the surface. This allows us to gain unprecedented information about the distribution and local configuration of the adsorbed reactants on the catalyst's surface during the CO oxidation reaction, which may serve as benchmarks for future k-MC simulations. Under reaction conditions the catalyst surface exposes areas which are catalytically active and areas which are poisoned by densely packed bridging CO and on-top CO. The actual reaction proceeds via the so-called Langmuir-Hinshelwood mechanism in that neighboring on-top O and on-top CO preferentially recombine to form CO 2 . The thermally induced restoration of the mildly reduced RuO 2 (110) surface was studied in situ on the atomic scale.

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