Photodissociation of methyl iodide adsorbed on low-temperature amorphous ice surfaces

Journal Article · Thu Feb 28 00:00:00 EST 2013 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4790585· OSTI ID:22105392

DeSimone, Alice J.; Olanrewaju, Babajide O.; Grieves, Gregory A. ^[1]; Orlando, Thomas M. ^[1]

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1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 (United States)

Photodissociation dynamics of methyl iodide (CH{sub 3}I) adsorbed on both amorphous solid water (ASW) and porous amorphous solid water (PASW) has been investigated. The ejected ground-state I({sup 2}P{sub 3/2}) and excited-state I({sup 2}P{sub 1/2}) photofragments produced by 260- and 290-nm photons were detected using laser resonance-enhanced multiphoton ionization. In contrast to gas-phase photodissociation, (i) the I({sup 2}P{sub 3/2}) photofragment is favored compared to I({sup 2}P{sub 1/2}) at both wavelengths, (ii) I({sup 2}P{sub 3/2}) and I({sup 2}P{sub 1/2}) have velocity distributions that depend upon ice morphology, and (iii) I{sub 2} is produced on ASW. The total iodine [I({sup 2}P{sub 3/2})+I({sup 2}P{sub 1/2})+I{sub 2}] yield varies with substrate morphology, with greater yield from ASW than PASW using both 260- and 290-nm photons. Temperature-programmed desorption studies demonstrate that ice porosity enhances the trapping of adsorbed CH{sub 3}I, while pore-free ice likely allows monomer adsorption and the formation of two-dimensional CH{sub 3}I clusters. Reactions or collisions involving these clusters, I atomic fragments, or I-containing molecular fragments at the vacuum-surface interface can result in I{sub 2} formation.

• OSTI ID: 22105392
• Journal Information: Journal of Chemical Physics, Vol. 138, Issue 8; Other Information: (c) 2013 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ADSORPTION
AMORPHOUS STATE
DESORPTION
DISSOCIATION
EXCITED STATES
GROUND STATES
INTERFACES
IODINE
METHYL IODIDE
MORPHOLOGY
MULTI-PHOTON PROCESSES
PHOTOIONIZATION
PHOTOLYSIS
PHOTON-MOLECULE COLLISIONS
SOLIDS
SUBSTRATES
SURFACES
TWO-DIMENSIONAL CALCULATIONS