Molecular Dynamics of the Electron-Induced Reaction of Diiodomethane on Cu(110)

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• 作者：Avisek Chatterjee ; Fang Cheng ; Lydie Leung ; Miaomiao Luo ; Zhanyu Ning ; John C. Polanyi
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：November 6, 2014
• 年：2014
• 卷：118
• 期：44
• 页码：25525-25533
• 全文大小：505K
• ISSN：1932-7455

文摘

Diiodomethane is used to generate C₁ fragments at surfaces, en route to higher hydrocarbons. Here scanning tunneling microscopy was employed to examine the interaction of diiodomethane, CH₂I₂, with a Cu(110) surface, from 4.6 to 8.8 K. In this temperature range unexpectedly rapid thermal reaction resulted in the rupture of two C鈥揑 bonds, yielding pairs of I atoms recoiling in opposite directions. Approximately 65% of the carbene, CH₂, product from this highly exothermic (4.1 eV) thermal reaction remained chemisorbed. Two stable physisorbed configurations of diiodomethane were found, 鈥渧ertical鈥?(75%) and 鈥渉orizontal鈥?(25%). Electron-induced reaction of these intact adsorbates led to single-electron dissociation of both the C鈥揑 bonds, with a minor path leading to single bond breaking to form CH₂I. Directed recoil of chemisorbed carbene was observed in approximately half the electron-induced reactive events. Simulation of the electron-induced reaction by the impulsive two-state (I2S) model consistently predicted delayed dissociation of the second C鈥揑 bond, due to vibrational excitation of the CH₂I radical product. Theory and experiment agreed in evidencing long-range recoil for the CH₂ along the [11虆0] direction of the copper. This recoiling diradical was shown by the I2S model to undergo migration by a novel process of 鈥渨alking鈥?along a pair of adjacent copper rows.