Normal Modes at Surfaces

Richardson, N.V.; Sheppard, N.

doi:10.1007/978-1-4684-8759-6_1

Cited by 17 publications

(11 citation statements)

References 56 publications

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“…In the case of adsorption, if the overlayer is ordered and has a smaller surface Brillouin zone ͑SBZ͒ compared with the substrate SBZ, some substrate phonon modes can be folded back to ⌫ from the high symmetry points of the substrate SBZ and may become observable in specular geometry if they are dipole active. [22][23][24] This quite general phenomenon is also observed for the O-Ru͑0001͒ system as discussed in the following.…”

Section: Quenching Of the Lower Symmetry Derived Modessupporting

confidence: 66%

Vibrational analysis of the 1×1-O overlayer on Ru(0001)

Jacobi

1997

Phys. Rev. B

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A densely packed 1ϫ1-O overlayer with an oxygen coverage of 1.0 ͑relative to the number of substrate surface atoms͒ was prepared on Ru͑0001͒ by sequential dissociation of O 2 and NO 2 and studied by means of high-resolution electron-energy-loss spectroscopy. Two dipole-active modes were observed at 81 and 7.3 meV due to a Ќ (Ru-O) stretch mode and a new surface mode, respectively. The value of Ќ (Ru-O) is shifted to higher energy compared to that for the known 2ϫ2-O and 2ϫ1-O adlayers at smaller oxygen coverages. These measurements indicate that the O 2 dissociation is kinetically hindered for oxygen coverages larger than 0.5.

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Section: Quenching Of the Lower Symmetry Derived Modessupporting

confidence: 66%

Vibrational analysis of the 1×1-O overlayer on Ru(0001)

Jacobi

1997

Phys. Rev. B

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“…39,40 When the C-O stretching bands (both of which possess similar strong infrared absorption cross sections but orthogonal dynamic dipole moments in the free state) are used as a guide, the fact that ν s (OCO) is infraredactive while ν as (OCO) is not implies that all three species adopt upright, symmetrical bidentate bridging configurations with C 2V symmetry. Similar conclusions have been reached for the analogous cases on Ag{110}.…”

Section: Structures Of the Stable Intermediates On Ag{111}mentioning

confidence: 99%

Mechanism of Acetone Oxidation on Ag{111}-p(4 × 4)−O

and

King

1996

J. Phys. Chem.

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The decomposition of acetone over preoxidized Ag{111} has been studied using reflection absorption infrared spectroscopy. Propane-2,2-diyldioxy and acetone enolate are formed through O-induced nucleophilic addition and H abstraction at 180 K. Further oxidation occurs rapidly above 220 K via acetone enolate to yield metallacyclic intermediates that break down into ketene and methylenedioxy, which deprotonate to produce stable ketenylidene and formate, respectively. The measured vibrational frequencies of several surface-bound ketenylidene isotopomers have been successfully fit to a modified valence force field analysis. Although ketenylidene and CO adsorbed on a metal surface both exhibit strong absorption features due to ν op (CCO) and ν(CO), respectively, at ∼2000 cm -1 in their vibrational spectra, it is shown that they may still be readily distinguished by selective 13 C or 18 O substitution of their carbonyl atoms only, since this results in pairs of absorption bands that possess frequencies of the opposite order (ν op (C 13 CO) < ν op (CC 18 O) and ν(C 18 O) < ν( 13 CO)). A reaction mechanism has been proposed that accounts for the fact that ketenylidene retains the acetone carbonyl group while formate is wholly derived from the acetone methyl group.

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“…If we consider the number of vibrational modes available for vibrational excitation, these are 3N Ϫ6 for a nonlinear N-atom species; for linear species these are 3NϪ5. 47 Clearly, more internal modes are available for molecules which are composed of more atoms. ͑3͒ There may be steric requirements for translational-tointernal energy transfer to occur.…”

Section: B Internal Energy Uptake Efficaciesmentioning

confidence: 99%