کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5423726 | 1507949 | 2010 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Photochemistry of methyl bromide on the α-Cr2O3(0001) surface
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Photochemistry of methyl bromide on the α-Cr2O3(0001) surface Photochemistry of methyl bromide on the α-Cr2O3(0001) surface](/preview/png/5423726.png)
چکیده انگلیسی
The photochemical properties of the Cr-terminated α-Cr2O3(0001) surface were explored using methyl bromide (CH3Br) as a probe molecule. CH3Br adsorbed and desorbed molecularly from the Cr-terminated α-Cr2O3(0001) surface without detectable thermal decomposition. Temperature programmed desorption (TPD) revealed a CH3Br desorption state at 240 K for coverages up to 0.5 ML, followed by more weakly bound molecules desorbing at 175 K for coverages up to 1 ML. Multilayer exposures led to desorption at ~ 130 K. The CH3Br sticking coefficient was unity at 105 K for coverages up to monolayer saturation, but decreased as the multilayer formed. In contrast, pre-oxidation of the surface (using an oxygen plasma source) led to capping of surface Cr3+ sites and near complete removal of CH3Br TPD states above 150 K. The photochemistry of chemisorbed CH3Br was explored on the Cr-terminated surface using post-irradiation TPD and photon stimulated desorption (PSD). Irradiation of adsorbed CH3Br with broad band light from a Hg arc lamp resulted in both photodesorption and photodecomposition of the parent molecule at a combined cross section of ~ 10â 22 cm2. Photodissociation of the CH3-Br bond was evidenced by both CH3 detected in PSD and Br atoms left on the surface. Use of a 385 nm cut-off filter effectively shut down the photodissociation pathway but not the parent molecule photodesorption process. From these observations it is inferred that d-to-d transitions in α-Cr2O3, occurring at photon energies < 3 eV, do not significantly promote photodecomposition of adsorbed CH3Br. It is unclear to what extent band-to-band versus direct CH3Br photolysis play in CH3-Br bond dissociation initiated by more energetic photons.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Surface Science - Volume 604, Issues 19â20, September 2010, Pages 1800-1807
Journal: Surface Science - Volume 604, Issues 19â20, September 2010, Pages 1800-1807
نویسندگان
Michael A. Henderson,