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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 7
BKCSDE 30(7)
July 20, 2009 

 
Title
Thermal and Photochemistry of Methyl Iodide on Ice Film Grown on Cu(111)
Author
Youngku Sohn*, John M White
Keywords
Temperature-programmed desorption, X-ray photoelectron spectroscopy, Photo-dissociation, Solvated electron, Diffusion
Abstract
Thermal and photochemistry of methyl iodide (CH3I) adsorbed on D2O ice film on Cu(111) at 100 K were studied using temperature-programmed desorption (TPD) time-of-flight mass spectrometry (TOF-MS), X-ray and ultraviolet photoelectron spectroscopies. On the basis of TPD, multilayer and monolayer CH3I molecules desorb from D2O ice layer at 120 and 130 K, respectively. Photo-irradiation at 100 K exhibits dramatic changes in the TPD and I 3d5/2 XPS of CH3I on ice film, due to a dramatic dissociation of CH3I. The dissociation is likely activated by solvated electrons transferred from the metal substrate during photo-irradiation. No other photo-initiated reaction products were found within our instrumental detection limit. During photo-irradiation, the CH3I, CH3 and I could be trapped (or solvated) in ice film by rearrangement (and self-diffusion) of water molecules. A newly appeared parent molecular desorption peak at 145 K is attributed to trapped CH3I. In addition, the CH3 and I may diffuse through ice and chemisorb on Cu(111), indicated by TPD and I 3d5/2 XPS taken with photo-irradiation time, respectively. No molecular ejection was found during photo-irradiation at 100 K. The work functions for CH3I/Cu(111), D2O/Cu (111) and CH3I/D2O/Cu(111) were all measured to be about 3.9 eV, 1.0 eV downward shift from that of clean Cu(111).
Page
1470 - 1474
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