Hyperthermal velocity distributions of recombinatively-desorbing oxygen from Ag(111).

This study presents velocity-resolved desorption experiments of recombinatively-desorbing oxygen from Ag (111). We combine molecular beam techniques, ion imaging, and temperature-programmed desorption to obtain translational energy distributions of desorbing O2. Molecular beams of NO2 are used to prepare a p (4 × 4)-O adlayer on the silver crystal. The translational energy distributions of O2 are shifted towards hyperthermal energies indicating desorption from an intermediate activated molecular chemisorption state.

Raising the benchmark potential of a simple alcohol-ketone intermolecular balance.

2-Butanone offers two hydrogen bond docking variants to a solvating methanol which are cleanly separated by supersonic jet infrared absorption spectroscopy in the OH-stretching range, resolving earlier action spectroscopy indeterminacies for this elementary case of an intermolecular alcohol-ketone balance. The solvent preference for the shorter chain side is unambiguously derived from the spectra of homologous compounds. It is analysed in terms of competing steric and dispersion interactions and the resulting energy differences across a low interconversion barrier. Fortuitous cancellations are discussed and quantitative energy deficiencies of the employed DFT approaches are suggested. Some benchmarkable experimental observations: at low temperature, a single methanol molecule prefers the methyl-sided oxygen lone pair of 2-butanone over the ethyl-sided lone pair by 1-2 kJ mol-1, the trans butane backbone is conserved in both low-lying isomers, the OH-stretching fundamentals differ by 47(2) cm-1.

Velocity map images of desorbing oxygen from sub-surface states of Rh(111).

We combine velocity map imaging (VMI) with temperature-programmed desorption (TPD) experiments to record the angular-resolved velocity distributions of recombinatively-desorbing oxygen from Rh(111). We assign the velocity distributions to desorption from specific surface and sub-surface states by matching the recorded distributions to the desorption temperature. These results provide insight into the recombinative desorption mechanisms and the availability of oxygen for surface-catalyzed reactions.