State-resolved reactivity of CH4 on Pt(110)-(1x2): The role of surface orientation and impact site
State-resolved reactivity of CH4 on Pt(110)-(1x2): The role of surface orientation and impact site
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DOI：
10.1063/1.3328885
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发表时间：
2010-03-07
影响因子：
4.4
通讯作者：
Beck, Rainer D.
中科院分区：
文献类型：
--
作者：
Bisson, Regis;Sacchi, Marco;Beck, Rainer D.
用量子态分辨表面反应性测量方法研究了甲烷在Pt（110）-（1x 2）表面上的反应性。在4-64 kJ/mol的入射平动能范围内，测量了CH_4在反对称C-H伸缩振动的第一泛音（2 nu（3））激发下的基态反应几率S-0（v=0）与S-0（laser-off）一致，以及态分辨反应几率S-0（2 nu（3））.我们观察到S-0（2 nu（3））比S-0（v=0）高出三个数量级，这表明2 nu（3）激发对Pt（110）-（1x 2）上CH 4解离的显着振动激活。此外，我们探讨了方位角和极入射角的依赖性的S-0（2 nu（3））和S-0（v=0）的一个固定的入射平移能E-t=32 kJ/mol。对于垂直于Pt（110）-（1x 2）上的缺失行方向的入射和极角θ>40度，遮蔽效应防止入射CH 4分子撞击到槽位点。将这种极角依赖性与平行于缺失行入射的反应性数据进行比较，得到了与Pt（110）-（1x 2）反应性一致的状态分辨位点特异性反应性信息，该反应性由位于脊位点的顶层Pt原子主导。在Pt（110）-（1x 2）和Pt（111）上测量的S-0（v=0）的比较产生Pt（110）-（1x 2）的较低平均势垒13.7 +/- 2.0 kJ/mol。
The reactivity of methane (CH4) on Pt(110)-(1x2) has been studied by quantum state-resolved surface reactivity measurements. Ground state reaction probabilities, S-0(v=0)congruent to S-0(laser-off), as well as state-resolved reaction probabilities S-0(2 nu(3)), for CH4 excited to the first overtone of the antisymmetric C-H stretch (2 nu(3)) have been measured at incident translational energies in the range of 4-64 kJ/mol. We observe S-0(2 nu(3)) to be up to three orders of magnitude higher than S-0(v=0), demonstrating significant vibrational activation of CH4 dissociation on Pt(110)-(1x2) by 2 nu(3) excitation. Furthermore, we explored the azimuthal and polar incident angle dependence of S-0(2 nu(3)) and S-0(v=0) for a fixed incident translational energy E-t=32 kJ/mol. For incidence perpendicular to the missing row direction on Pt(110)-(1x2) and polar angles theta>40 degrees, shadowing effects prevent the incident CH4 molecules from impinging into the trough sites. Comparison of this polar angle dependence with reactivity data for incidence parallel to the missing rows yields state-resolved site specific reactivity information consistent with a Pt(110)-(1x2) reactivity that is dominated by top layer Pt atoms located at the ridge sites. A comparison of S-0(v=0) measured on Pt(110)-(1x2) and Pt(111) yields a lower average barrier for Pt(110)-(1x2) by 13.7 +/- 2.0 kJ/mol.