Rockey Thomas J, Yang Minchul, Dai Hai-Lung
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
J Phys Chem B. 2006 Oct 12;110(40):19973-8. doi: 10.1021/jp062225n.
The adsorption of monolayer and multilayer benzene on the Ag(111) surface was characterized using temperature programmed desorption (TPD). TPD spectra revealed two broad peaks at approximately 205 and approximately 150 K at submonolayer coverage and a sharper, multilayer peak at 140 K. Analysis of the coverage-dependent shape and shift of the two submonolayer peaks has resulted in their assignment to desorption from two different binding geometries on threefold-hollow sites with symmetries C(3v)(sigma d) and C(3v)(sigma v). The TPD peak analysis incorporated inter-adsorbate repulsive interaction that resulted from the local dipole moment at the adsorption site induced by the adsorbate-surface charge transfer bonding. The analysis has yielded desorption energies of 54.9 +/- 0.8 and 50.4 +/- 0.4 kJ/mol for the C(3v)(sigma d) and C(3v)(sigma v) configurations, respectively. The interface dipole and polarizability of the benzene-silver complex have been determined to be 5.4 +/- 1.8 D and 14 +/- 10 A3, respectively. Repulsive interactions in the monolayer were found to lower the desorption energy from the zero-coverage value by 14.8 kJ/mol. Leading edge analysis of the multilayer peak yielded a desorption energy of 40.9 +/- 0.7 kJ/mol.
采用程序升温脱附（TPD）对单层和多层苯在Ag(111)表面的吸附进行了表征。TPD谱显示，在亚单层覆盖时，大约在205 K和大约150 K处有两个宽峰，在140 K处有一个更尖锐的多层峰。对两个亚单层峰的覆盖度依赖形状和位移进行分析，结果表明它们分别对应于在具有C(3v)(σd)和C(3v)(σv)对称性的三重空穴位点上从两种不同结合几何结构的脱附。TPD峰分析考虑了吸附质间的排斥相互作用，这种相互作用是由吸附质-表面电荷转移键在吸附位点诱导的局部偶极矩引起的。分析得出，对于C(3v)(σd)和C(3v)(σv)构型，脱附能分别为54.9±0.8 kJ/mol和50.4±0.4 kJ/mol。已确定苯-银络合物的界面偶极和极化率分别为5.4±1.8 D和14±10 ų。发现单层中的排斥相互作用使脱附能从零覆盖值降低了14.8 kJ/mol。多层峰的前沿分析得出脱附能为40.9±0.7 kJ/mol。
