257 nm photoinduced chemistry of methyl iodide adsorbed on MgO(100)

K. A. Trentelman, D. H. Fairbrother, P. G. Strupp, Peter C Stair, Eric Weitz

Research output: Contribution to journalArticle

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Abstract

The 257 nm photochemistry of CD3I adsorbed on MgO(100) has been investigated. The photofragments ejected along the surface normal were probed using resonantly enhanced multiphoton ionization spectroscopy coupled with time-of-flight mass spectrometry. Methyl radicals and atomic iodine fragments in both the ground I(2P3/2)≡I and spin-orbit excited I(2P1/2)≡I* states were observed as direct photofragments produced at the surface. Laser-induced desorption of methyl iodide competes with dissociation at the surface. The total cross section for removal of adsorbed CD3I from the surface at 257 nm is comparable to the gas phase cross section. A significant portion of the atomic iodine fragments remain trapped at the surface with preferential trapping of I*. Additionally, nonresonant I+ and I2 + signals were detected and initially observed to increase as a function of the irradiation time and then decrease with further irradiation. This behavior is shown to be indicative of photoinduced production and photoinduced removal of a surface intermediate. A surface reaction mechanism and the existence of a common precursor resulting from the interaction of adsorbed atomic iodine with adsorbed methyl iodide or methyl iodide clusters is postulated.

Original languageEnglish
Pages (from-to)9221-9232
Number of pages12
JournalJournal of Chemical Physics
Volume96
Issue number12
Publication statusPublished - 1992

Fingerprint

iodides
chemistry
Iodine
iodine
fragments
Irradiation
irradiation
Photochemical reactions
cross sections
Surface reactions
photochemical reactions
surface reactions
Ionization
Mass spectrometry
methyl iodide
Desorption
Orbits
mass spectroscopy
Gases
desorption

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Trentelman, K. A., Fairbrother, D. H., Strupp, P. G., Stair, P. C., & Weitz, E. (1992). 257 nm photoinduced chemistry of methyl iodide adsorbed on MgO(100). Journal of Chemical Physics, 96(12), 9221-9232.

257 nm photoinduced chemistry of methyl iodide adsorbed on MgO(100). / Trentelman, K. A.; Fairbrother, D. H.; Strupp, P. G.; Stair, Peter C; Weitz, Eric.

In: Journal of Chemical Physics, Vol. 96, No. 12, 1992, p. 9221-9232.

Research output: Contribution to journalArticle

Trentelman, KA, Fairbrother, DH, Strupp, PG, Stair, PC & Weitz, E 1992, '257 nm photoinduced chemistry of methyl iodide adsorbed on MgO(100)', Journal of Chemical Physics, vol. 96, no. 12, pp. 9221-9232.
Trentelman KA, Fairbrother DH, Strupp PG, Stair PC, Weitz E. 257 nm photoinduced chemistry of methyl iodide adsorbed on MgO(100). Journal of Chemical Physics. 1992;96(12):9221-9232.
Trentelman, K. A. ; Fairbrother, D. H. ; Strupp, P. G. ; Stair, Peter C ; Weitz, Eric. / 257 nm photoinduced chemistry of methyl iodide adsorbed on MgO(100). In: Journal of Chemical Physics. 1992 ; Vol. 96, No. 12. pp. 9221-9232.
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N2 - The 257 nm photochemistry of CD3I adsorbed on MgO(100) has been investigated. The photofragments ejected along the surface normal were probed using resonantly enhanced multiphoton ionization spectroscopy coupled with time-of-flight mass spectrometry. Methyl radicals and atomic iodine fragments in both the ground I(2P3/2)≡I and spin-orbit excited I(2P1/2)≡I* states were observed as direct photofragments produced at the surface. Laser-induced desorption of methyl iodide competes with dissociation at the surface. The total cross section for removal of adsorbed CD3I from the surface at 257 nm is comparable to the gas phase cross section. A significant portion of the atomic iodine fragments remain trapped at the surface with preferential trapping of I*. Additionally, nonresonant I+ and I2 + signals were detected and initially observed to increase as a function of the irradiation time and then decrease with further irradiation. This behavior is shown to be indicative of photoinduced production and photoinduced removal of a surface intermediate. A surface reaction mechanism and the existence of a common precursor resulting from the interaction of adsorbed atomic iodine with adsorbed methyl iodide or methyl iodide clusters is postulated.

AB - The 257 nm photochemistry of CD3I adsorbed on MgO(100) has been investigated. The photofragments ejected along the surface normal were probed using resonantly enhanced multiphoton ionization spectroscopy coupled with time-of-flight mass spectrometry. Methyl radicals and atomic iodine fragments in both the ground I(2P3/2)≡I and spin-orbit excited I(2P1/2)≡I* states were observed as direct photofragments produced at the surface. Laser-induced desorption of methyl iodide competes with dissociation at the surface. The total cross section for removal of adsorbed CD3I from the surface at 257 nm is comparable to the gas phase cross section. A significant portion of the atomic iodine fragments remain trapped at the surface with preferential trapping of I*. Additionally, nonresonant I+ and I2 + signals were detected and initially observed to increase as a function of the irradiation time and then decrease with further irradiation. This behavior is shown to be indicative of photoinduced production and photoinduced removal of a surface intermediate. A surface reaction mechanism and the existence of a common precursor resulting from the interaction of adsorbed atomic iodine with adsorbed methyl iodide or methyl iodide clusters is postulated.

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