Photochemistry of methyl bromide adsorbed on platinum(111)

Costello, S. A.; Roop, B.; Liu, Z.-M.; White, J. M.

doi:10.1021/j100316a006

Cited by 97 publications

(24 citation statements)

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“…However, neither photodissociation products nor the parent molecule were detected, independent on the pump–probe delay time. Similar results were reported by White and coworkers for methyl iodide adsorbed on Pt(111) [ 28 – 31 ]. In their work, methyl iodide molecules that were adsorbed on the metal surface were exposed to the full spectrum of an Hg arc lamp.…”

Section: Resultssupporting

confidence: 90%

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Vaida¹,

Tchitnga²,

Bernhardt³

2011

Beilstein J. Nanotechnol.

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SummaryThe photodissociation of small organic molecules, namely methyl iodide, methyl bromide, and methyl chloride, adsorbed on a metal surface was investigated in real time by means of femtosecond-laser pump–probe mass spectrometry. A weakly interacting gold surface was employed as substrate because the intact adsorption of the methyl halide molecules was desired prior to photoexcitation. The gold surface was prepared as an ultrathin film on Mo(100). The molecular adsorption behavior was characterized by coverage dependent temperature programmed desorption spectroscopy. Submonolayer preparations were irradiated with UV light of 266 nm wavelength and the subsequently emerging methyl fragments were probed by photoionization and mass spectrometric detection. A strong dependence of the excitation mechanism and the light-induced dynamics on the type of molecule was observed. Possible photoexcitation mechanisms included direct photoexcitation to the dissociative A-band of the methyl halide molecules as well as the attachment of surface-emitted electrons with transient negative ion formation and subsequent molecular fragmentation. Both reaction pathways were energetically possible in the case of methyl iodide, yet, no methyl fragments were observed. As a likely explanation, the rapid quenching of the excited states prior to fragmentation is proposed. This quenching mechanism could be prevented by modification of the gold surface through pre-adsorption of iodine atoms. In contrast, the A-band of methyl bromide was not energetically directly accessible through 266 nm excitation. Nevertheless, the one-photon-induced dissociation was observed in the case of methyl bromide. This was interpreted as being due to a considerable energetic down-shift of the electronic A-band states of methyl bromide by about 1.5 eV through interaction with the gold substrate. Finally, for methyl chloride no photofragmentation could be detected at all.

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Section: Resultssupporting

confidence: 90%

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Vaida¹,

Tchitnga²,

Bernhardt³

2011

Beilstein J. Nanotechnol.

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“…5,9 Experimental evidence in support of enhanced photochemistry can be found in studies of various types of molecules on silver surfaces. [10][11][12][13][14][15][16][17][18] As in the photoemission studies cited above, the wavelength dependence of the photochemical reactions was often shown to track the plasmon resonance of silver. However, in the case of the photochemical reduction of p-nitrobenzoic acid, a charge transfer mechanism was proposed to rationalize the dependence of the photolysis rate as a function of photon flux, excitation energy, electrode potential, and the nature of the solvent.…”

Section: Introductionmentioning

confidence: 99%

Photoreduction of Methylviologen Adsorbed on Silver

1996

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Methylviologen adsorbed on a roughened silver electrode is reduced to its cation radical upon irradiation with laser light at liquid nitrogen temperature. Surface-enhanced Raman scattering (SERS) spectra were obtained with different excitation wavelengths between 406 and 752 nm and compared to those obtained at room temperature in an electrochemical cell under potential control. From two-color experiments, in which one laser frequency was used to generate the radical and a second to excite the SERS spectra, it was determined that radical formation occurs mainly with excitation in the blue spectral region. A comparison of the SERS spectra of the dication and cation radical forms of methylviologen with their solution spectra suggests that the former interacts more strongly with the surface than the latter. The cation radical appears to be stable for several hours in liquid nitrogen but has a short lifetime at room temperature. Two mechanisms for the photoreduction are discussed: plasmon-assisted electron transfer from the metal to the methylviologen dication and formation of a resonance charge transfer complex. The current experimental data are insufficient to determine the particular role of these mechanisms.

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“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16] Both thermal and photochemical processing of such adsorbates results in the production of adsorbed alkyl moieties, although in the presence of coadsorbed halogen atoms. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Both thermal and photochemical processing of such adsorbates results in the production of adsorbed alkyl moieties, although in the presence of coadsorbed halogen atoms.…”

Section: Introductionmentioning

confidence: 99%

The chemistry of simple alkyl species on Pt(111) generated by hyperthermal collisions

Oakes¹,

Newell²,

Rutten³

et al. 1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Kinetics and dynamics of the trappingmediated dissociative chemisorption of oxygen on Ru (001) The identification of the primary dissociation products of hyperthermal collisions of methane and ethane with a Pt͑111͒ surface at ϳ150 K and the study of their subsequent thermal evolution has been afforded by the use of reflection-absorption infrared spectroscopy, temperature programmed desorption, and Auger electron spectroscopy. In both cases, the primary dissociation products have been identified as an adsorbed alkyl moiety ͑methyl, CH 3 , and ethyl, C 2 H 5 , respectively͒ and an adsorbed hydrogen atom. The thermal treatment of both alkyl adlayers ultimately results in the formation of the ethylidyne ͑wCCH 3 ͒ moiety at temperatures between 300 and 400 K. At ϳ500 K, this species itself thermally decomposes to yield adsorbed carbon atoms and gaseous hydrogen. While this behavior may not be unexpected for the C 2 ethyl fragment, the formation of the C 2 ethylidyne fragment from the C 1 methyl fragment can only be explained through the occurrence of carbon-carbon coupling reactions. Such reactions have only recently been observed on the Pt͑111͒ surface. The C-C coupling reactions associated with the formation of ethylidyne from methyl show considerable dependence upon the surface coverage of the methyl fragment and are accompanied by the evolution of both gaseous hydrogen and methane. The latter results from recombinative desorption of methyl moieties with adsorbed hydrogen atoms.

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Photochemistry of methyl bromide adsorbed on platinum(111)

Cited by 97 publications

References 0 publications

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Photoreduction of Methylviologen Adsorbed on Silver

The chemistry of simple alkyl species on Pt(111) generated by hyperthermal collisions

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