The Crystal Structures of Methyl Bromide and Methyl Iodide

Kawaguchi, Takemi; Hijikigawa, Masaya; Hayafuji, Yoshinori; Ikeda, Masashi; Fukushima, Reizo; Tomiie, Yujiro

doi:10.1246/bcsj.46.53

Cited by 91 publications

(64 citation statements)

References 9 publications

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“…The density of the crystalline CH 3 Br in the (001) plane is 6.96 × 10 14 molecules/cm 2 , as obtained from X-ray studies. 21 Thus, it was concluded that upon completion of the first layer the density reaches 52 ( 5% and 58 ( 5%, respectively, of it's value in the bulk. We note that our interpretation of a monolayer is different from other studies [2][3][4]7 for which the definition of 1ML is correlated with a definition of a bilayer (2ML) in the present study.…”

Section: Resultsmentioning

confidence: 97%

Photoinduced Fragmentation of Multilayer CH₃Br on Cu/Ru(001)

Livneh¹,

Asscher²

2003

J. Phys. Chem. B

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The broadband UV (230-420 nm) photoinduced chemistry of CH 3 Br adsorbed on Cu(2ML)/Ru(001) in the coverage range of 1-50 ML was studied by monitoring the desorption products (∆p-TPD mode) in combination with post irradiation work function change measurements before and during surface heating (∆ -ΤPD mode). ∆ measurements enabled us to follow multilayer restructure and desorption of parent molecules and photochemical reaction products in the temperature range of 80-700 K. Methyl radicals accumulated on the surface are the precursor for the thermal formation of methane and ethylene at 450 K. Dehydrogenation of the methyl group is the rate-limiting step of the surface reaction resulting in the formation of these molecules. Based on work function change measurements, an estimate of the adsorbed methyl dipole moment is µ 0 ) 0.48 D. Dissociative electron attachment (DEA) driven CH 3 Br dissociation produced CH 3 and CH 2 fragments within the parent molecules multilayer matrix. At the multilayer coverage range, ∆ increases by up to 1.1 eV after 10 min UV irradiation. Model calculations qualitatively describe the post irradiation work function changes induced by the embedded photofragments (mostly Br -ions) inside the CH 3 Br dielectric film.Comparison of the ∆ -TPD spectra on Cu(2ML)/Ru(001) to those on clean Ru(001) indicates that the nature of the molecule-surface interaction and the structure of the first few layers strongly influence the resulting photochemistry at layer thickness up to at least 20 ML.

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Section: Resultsmentioning

confidence: 97%

Photoinduced Fragmentation of Multilayer CH₃Br on Cu/Ru(001)

Livneh¹,

Asscher²

2003

J. Phys. Chem. B

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“…Carbon atoms C1 and C2 show a slightly distorted tetrahedral coordination due to the different size of the surrounding atoms. The C-Br bond lengths of 1.938(4) and 1.924(4) Å, respectively, are in the region of C-Br bond lengths observed for methyl bromide [1.86(4) Å] [16] and dibromomethane (1.91 Å). [17] The C-F bond lengths of 1.377(4) and 1.356(4) Å, respectively, are in the region typical of C-F single bonds.…”

Section: Introductionmentioning

confidence: 81%

Crystal Structure and Spectroscopic Investigation of Bromofluoro‐ and Fluoroiodomethane

2015

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“…29,30 It turns out that on the copper-covered surface destabilization of the third layer is not observed. On the basis of the work function change spectrum during adsorption, we conclude that on the Cu(2 ML)/Ru(001) surface, CH 3 Br molecules cannot form a structure according to the molecular crystalline antiparallel arrangement 34 as well as on the clean Ru(001) surface. This may be related to the fact that on this surface there are more defects, and as a result, molecules adsorb in a distribution of tilt angles with respect to the normal to the surface.…”

Section: Ch 3 Br On Cu(2 Ml)/ru(001)mentioning

confidence: 92%

Surface Chemistry of CH₃Br and Methyl Modified by Copper Deposition on Ru(001)

Livneh

Asscher

1999

J. Phys. Chem. B

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The chemistry of methyl bromide on Cu/Ru(001) has been studied utilizing work function change (∆ ) and temperature-programmed desorption (TPD) measurements. The remarkable modification in the methyl fragments dehydrogenation at the completion of a single copper layer and the significant difference in reactivity of the Cu(2 ML)/Ru(001) or Cu(111) surfaces are the focus of this study. A decrease in work function at the completion of 1 ML CH 3 Br of 2.15 ( 0.02 eV and 1.33 ( 0.05 eV was measured, respectively, for Ru (001) and Cu(2 ML)/Ru(001) held at 82 K. Methyl bromide does not dissociate upon adsorption on clean or the copper-covered surfaces, and it is bound with the bromine down. Copper modifies the reactivity of the Ru substrate, gradually decreasing the dissociated fraction of CH 3 Br from 0.55 of the initial one monolayer on clean Ru(001) to 0.06 on Cu(2 ML)/Ru(001), probably because of defects in the copper layer. The methyl fragment dehydrogenation rate slows as the copper coverage increases. At a narrow copper coverage range between 0.8 and 0.95 ML, adsorbed hydrogen and methyl fragments coexist on the surface in the temperature range 230-280 K. Sequential decomposition channels of the parent molecules and the methyl fragment lead to a unique enhancement of methane production rate, this on the account of further hydrocarbon dehydrogenation, as reflected in both ∆p and ∆ TPD measurements. Methane is formed on top of copper terraces as a result of "spill-over" of both methyl and hydrogen atoms, similar to the chemistry over Cu(111) and Cu(110) single-crystal surfaces. The dipole moment of adsorbed methyl is reported here for the first time on metal surfaces, being 0.48 D on top of Cu(2 ML)/Ru(001).

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The Crystal Structures of Methyl Bromide and Methyl Iodide

Cited by 91 publications

References 9 publications

Photoinduced Fragmentation of Multilayer CH₃Br on Cu/Ru(001)

Photoinduced Fragmentation of Multilayer CH₃Br on Cu/Ru(001)

Crystal Structure and Spectroscopic Investigation of Bromofluoro‐ and Fluoroiodomethane

Surface Chemistry of CH₃Br and Methyl Modified by Copper Deposition on Ru(001)

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The Crystal Structures of Methyl Bromide and Methyl Iodide

Cited by 91 publications

References 9 publications

Photoinduced Fragmentation of Multilayer CH3Br on Cu/Ru(001)

Photoinduced Fragmentation of Multilayer CH3Br on Cu/Ru(001)

Crystal Structure and Spectroscopic Investigation of Bromofluoro‐ and Fluoroiodomethane

Surface Chemistry of CH3Br and Methyl Modified by Copper Deposition on Ru(001)

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Product

Resources

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Photoinduced Fragmentation of Multilayer CH₃Br on Cu/Ru(001)

Photoinduced Fragmentation of Multilayer CH₃Br on Cu/Ru(001)

Surface Chemistry of CH₃Br and Methyl Modified by Copper Deposition on Ru(001)