Kinetics of electron-induced decomposition of CF{sub 2}Cl{sub 2} coadsorbed with water (ice): A comparison with CCl{sub 4}

Journal Article · Mon Nov 01 04:00:00 EST 2004 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.1796551· OSTI ID:20658025

Faradzhev, N S; Perry, C C; Kusmierek, D O; Fairbrother, D H; Madey, T E ^[1]

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1. Department of Physics and Astronomy, and Laboratory for Surface Modification, Rutgers, State University of New Jersey, Piscataway, New Jersey 08854-8019 (United States)

The kinetics of decomposition and subsequent chemistry of adsorbed CF{sub 2}Cl{sub 2}, activated by low-energy electron irradiation, have been examined and compared with CCl{sub 4}. These molecules have been adsorbed alone and coadsorbed with water ice films of different thicknesses on metal surfaces (Ru; Au) at low temperatures (25 K; 100 K). The studies have been performed with temperature programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), and x-ray photoelectron spectroscopy (XPS). TPD data reveal the efficient decomposition of both halocarbon molecules under electron bombardment, which proceeds via dissociative electron attachment (DEA) of low-energy secondary electrons. The rates of CF{sub 2}Cl{sub 2} and CCl{sub 4} dissociation increase in an H{sub 2}O (D{sub 2}O) environment (2-3x), but the increase is smaller than that reported in recent literature. The highest initial cross sections for halocarbon decomposition coadsorbed with H{sub 2}O, using 180 eV incident electrons, are measured (using TPD) to be 1.0{+-}0.2x10{sup -15} cm{sup 2} for CF{sub 2}Cl{sub 2} and 2.5{+-}0.2x10{sup -15} cm{sup 2} for CCl{sub 4}. RAIRS and XPS studies confirm the decomposition of halocarbon molecules codeposited with water molecules, and provide insights into the irradiation products. Electron-induced generation of Cl{sup -} and F{sup -} anions in the halocarbon/water films and production of H{sub 3}O{sup +}, CO{sub 2}, and intermediate compounds COF{sub 2} (for CF{sub 2}Cl{sub 2}) and COCl{sub 2}, C{sub 2}Cl{sub 4} (for CCl{sub 4}) under electron irradiation have been detected using XPS, TPD, and RAIRS. The products and the decomposition kinetics are similar to those observed in our recent experiments involving x-ray photons as the source of ionizing irradiation.

• OSTI ID: 20658025
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 17 Vol. 121; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
CARBON DIOXIDE
CARBON TETRACHLORIDE
CHLORINE IONS
COBALT CHLORIDES
COBALT FLUORIDES
COMPARATIVE EVALUATIONS
CROSS SECTIONS
DECOMPOSITION
ELECTRON BEAMS
ELECTRONS
EV RANGE 100-1000
FLUORINE IONS
FREONS
GOLD
HEAVY WATER
INFRARED SPECTRA
IRRADIATION
OXONIUM IONS
PHOTONS
REACTION KINETICS
RUTHENIUM
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
X-RAY PHOTOELECTRON SPECTROSCOPY