Carbon-carbon coupling of methyl groups on Pt(111)

Fairbrother, D. Howard; Peng, Xiang; Viswanathan, R.; Stair, Peter C.; Trenary, Michael; Fan, Jian Chun

doi:10.1016/0039-6028(93)90900-5

Cited by 94 publications

(89 citation statements)

References 23 publications

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“…Ethylene formation from the surface reaction of CH 3(a) (without surface additives) was not observed on several metal surfaces [29][30][31][32][33].…”

Section: Adsorption Of Ch 3 and Its Reactionsmentioning

confidence: 95%

Infrared study of the adsorption of CO and CH3 on silica-supported MoO3 and Mo2C catalysts

Raskó¹

2003

Applied Catalysis A: General

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“…Ethylene formation from the surface reaction of CH 3(a) (without surface additives) was not observed on several metal surfaces [29][30][31][32][33].…”

Section: Adsorption Of Ch 3 and Its Reactionsmentioning

confidence: 95%

Infrared study of the adsorption of CO and CH3 on silica-supported MoO3 and Mo2C catalysts

Raskó¹

2003

Applied Catalysis A: General

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“…The problem associated with this approach is that it is impossible to avoid the influence of coadsorbed halogen atoms on the reaction pathways and kinetics of the radicals. Another means to generate the methyl radicals is by thermal decomposition of azomethane gas initially developed by Stair and co-workers [22][23][24] in the form of a nozzle source. The gaseous radicals can be directed onto a solid substrate maintained at a desirable temperature.…”

Section: Introductionmentioning

confidence: 99%

Chemisorption and Reaction Characteristics of Methyl Radicals on Cu(110)

et al. 2004

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Methyl radicals are generated by pyrolysis of azomethane, and the condition for achieving neat adsorption on Cu(110) is described for studying their chemisorption and reaction characteristics. The radical-surface system is examined by X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, temperature-programmed desorption, low-energy electron diffraction (LEED), and high-resolution electron energy loss spectroscopy under ultrahigh vacuum conditions. It is observed that a small fraction of impinging CH3 radicals decompose into methylene possibly on surface defect sites. This type of CH2 radical has no apparent effect on CH3(ads) surface chemistry initiated by dehydrogenation to form active CH2(ads) followed by chain reactions to yield high-mass alkyl products. All thermal desorption products, such as H2, CH4, C2H4, C2H6, and C3H6, are detected with a single desorption peak near 475 K. The product yields increase with surface coverage until saturation corresponding to 0.50 monolayer of CH3(ads). The mass distribution is, however, invariant with initial CH3(ads) coverage, and all desorbed species exhibit first-order reaction kinetics. LEED measurement reveals a c(2 × 2) adsorbate structure independent of the amount of gaseous exposure. This strongly suggests that the radicals aggregate into close-packed two-dimensional islands at any exposure. The islanding behavior can be correlated with the reaction kinetics and is deemed to be essential for the chain propagation reactions. Some relevant aspects of the CH3/Cu(111) system are also presented. The new results are compared with those of prior studies employing methyl halides as radical sources. Major differences are found in the product distribution and desorption kinetics, and these are attributed to the influence of surface halogen atoms present in those earlier investigations.

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“…In contrast to the pre-irradiation TPD result, the post-irradiation TPD result in Fig. 4b showed a depleted -desorption peak, while a new peak denoted as at around 260 K. The peak was attributed to the associative recombination of CH 3 and H. [44][45][46] Moreover, methyl and methane desorbed species were detected by use of a mass spectrometer and their kinetic energy distributions were measured. Thus, it was clear that methane dissociated into methyl and hydrogen as a result of the irradiation of 6.4-eV photons.…”

Section: Photochemistry Of Saturated Hydrocarbonsmentioning

confidence: 81%

Photochemistry and Photo-Induced Ultrafast Dynamics at Metal Surfaces

Matsumoto¹

2007

Bulletin of the Chemical Society of Japan

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This account describes excitation mechanisms and ultrafast nuclear dynamics at metal surfaces induced upon photon irradiation. After reviewing possible excitation mechanisms for photochemistry of adsorbates on metal surfaces, we discuss the ultra-violet photochemistry of saturated hydrocarbons, i.e., methane and cyclohexane, on metal surfaces. Although these alkanes in the gas phase do not absorb photons at %6 eV, CH bond dissociation takes place upon 6.4-eV photon irradiation on metal surfaces. Hybridization between CH antibonding orbitals of the alkanes and metal bands, forming a new band across the Fermi level, is proposed to be responsible for both the photochemistry and CH vibrational mode softening. Since electronic relaxation at metal surfaces takes place very rapidly, most of excited adsorbates do not proceed to dissociation and/or desorption, but rather they are vibrationally excited. To probe photo-induced nuclear motions in real time, we developed femtosecond (fs) time-resolved second harmonic generation spectroscopy on metal surfaces. This method was used to explore the dynamics of photo-excited coherent vibration at Pt(111) surfaces covered with alkali-metal atoms. Irradiation of fs pump-laser pulses induced coherent vibrational motions of the stretching vibration of alkali atoms with respect to the metal surface and the Rayleigh modes of the Pt surface, which manifest themselves in modulations of second harmonic intensity of probe pulses. We also demonstrated that selective excitation of a phonon mode can be achieved by using tailored light pulse trains.

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Carbon-carbon coupling of methyl groups on Pt(111)

Cited by 94 publications

References 23 publications

Infrared study of the adsorption of CO and CH3 on silica-supported MoO3 and Mo2C catalysts

Infrared study of the adsorption of CO and CH3 on silica-supported MoO3 and Mo2C catalysts

Chemisorption and Reaction Characteristics of Methyl Radicals on Cu(110)

Photochemistry and Photo-Induced Ultrafast Dynamics at Metal Surfaces

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