Adsorption States of NO2 over Water-Ice Films Formed on Au(111)

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• 作者：Shinri Sato ; Dai Yamaguchi ; Kikuko Nakagawa ; Yoshihiko Inoue ; Akihiro Yabushita ; and Masahiro Kawasaki
• 刊名：Langmuir
• 出版年：2000
• 出版时间：November 28, 2000
• 年：2000
• 卷：16
• 期：24
• 页码：9533 - 9538
• 全文大小：107K
• 年卷期：v.16,no.24(November 28, 2000)
• ISSN：1520-5827

文摘

The adsorption states of NO₂ over amorphous and crystalline water-ice films formed on an Au(111)surface have been studied in an ultrahigh vacuum system by the temperature programmed desorption(TPD) technique and IR absorption-reflection spectroscopy (IRAS). The ice films are prepared by depositionof gas phase water on the Au substrate at <100 K for amorphous ice and at 140 K for crystalline ice. Thesurface of amorphous ice is characterized by the high density of free OH, while that of crystalline ice ischaracterized by grain boundaries and the lack of free OH. TPD for pure ice shows only one desorptionpeak of H₂O, while after NO₂ adsorption on it an additional weak H₂O desorption peak appears at 185K. This higher-temperature peak is attributable to decomposition of NO₂-H₂O adducts. IRAS measurementsrevealed that NO₂ adsorbs on ice surfaces as N₂O₄ with D_2h symmetry and that neither N₂O₄ isomers suchas D-isomers nor NO_x (x = 1, 2, and 3) species are produced in the temperature range of 90-140 K.Interaction of the ice surfaces with NO₂ (N₂O₄) as well as orientation of N₂O₄ adsorbed on the ice surfacesare investigated as a function of temperature. Thermal decomposition of NO₂ adsorbed on the water-iceformed on an Au surface is reconfirmed, which has been reported by Wang and Koel (J. Phys. Chem. A1998, 102, 8573). A possible mechanism for the NO₂ decomposition is proposed.