Multiple Pathways of Dissociative Attachment: CH3Br on Si(100)-2脳1
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- 作者：Ting Bin Lim ; Iain R. McNab ; John C. Polanyi ; Hong Guo ; Wei Ji
- 刊名：Journal of the American Chemical Society
- 出版年：2011
- 出版时间：August 3, 2011
- 年：2011
- 卷：133
- 期：30
- 页码：11534-11539
- 全文大小：850K
- 年卷期：v.133,no.30(August 3, 2011)
- ISSN：1520-5126
文摘
We describe the dissociative attachment (DA) of methyl bromide to form chemisorbed CH3 and Br on a Si(100)-2脳1 surface at 270 K. The patterns of DA were studied experimentally by ultra-high vacuum scanning tunneling microscopy (STM) and interpreted by ab initio theory. The parent molecules were found to dissociate thermally by breaking the C鈥揃r bond, attaching the resulting fragments CH3 and Br at adjacent Si-atom sites. The observed DA resulted in three distinct attachment geometries: inter-row (IR, 88%), inter-dimer (ID, 11%), and on-dimer (OD, 1%). Ab initio computation agreed in predicting these three DA reaction pathways, with yields decreasing down the series, in accord with experiment. The three computed physisorption geometries, each of which correlated with a preferred outcome, IR, ID, or OD, exhibited similar heats of adsorption, the choice of pathway being governed by the energy barriers to DA chemisorption predicted to increase along the series: EIR = 0.48 eV, EID = 0.57 eV, and EOD = 0.63 eV.