Our high-resolution electron energy-loss measurements concern physisorbed H₂ and comprise differential cross sections for the excitation of the internal H₂ modes and the H₂-surface bonding mode and their combinations and extend over the electron impact energy range of the classical low-energy H₂ ${}^2\mathrm{\Sigma }_u$ resonance. Comparison with corresponding data for the excitation of the internal modes of gas phase H₂ reveals that strong elastic electron reflectivity from the Cu(100) substrate profoundly distorts the inelastic scattering pattern for physisorbed H₂. We find that this influence can be corrected for and that the resulting peak cross sections agree with the H₂ gas phase data, in accordance with theoretical predictions for the excitation of the internal H₂ vibration. We have used corrected cross sections for the rotational mode spectra of physisorbed H₂, HD, and D₂ in a model concerning electron induced desorption via rotation-translation energy conversion. These spectra include transitions from the ground state as well as excited levels of the physisorption potential well. H₂ and HD can desorb from all levels while D₂, for energetic reason, can only desorb from the excited levels. This model gives a satisfactory account of the observed desorption cross sections and predicts characteristic velocity distributions of the desorbing molecules. The cross section data for H₂ and HD reveals that direct bound-free transitions also contribute to the electron induced desorption.

中文翻译：

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激发和物理吸附的H的解吸₂经由${}^{\mathrm{2个}}\mathrm{\Sigma }_{\mathit{ü}}$ 电子散射共振

我们的高分辨率电子能量损耗测量涉及物理吸附的H _2，并且包括用于激励内部H ₂模和H ₂表面键合模及其组合的微分截面，并且扩展了经典低电子的电子冲击能范围-能量H ₂ ${}^{\mathrm{2个}}\mathrm{\Sigma }_{ü}$谐振。与用于气相H ₂的内部模式的激发的相应数据的比较表明，来自Cu（100）衬底的强弹性电子反射率极大地扭曲了物理吸附H ₂的非弹性散射模式。我们发现，可以根据内部H ₂振动激发的理论预测来校正这种影响，并使峰横截面与H ₂气相数据相符。我们对物理吸附的H ₂，HD和D ₂的旋转模式光谱使用了校正的横截面在涉及通过旋转-平移能量转换的电子诱导解吸的模型中。这些光谱包括从基态的跃迁以及物理吸附势阱的激发能级。H ₂和HD可以从所有能级上解吸，而D ₂出于能量原因只能从激发能级上解吸。该模型对观察到的解吸横截面给出了令人满意的解释，并预测了解吸分子的特征速度分布。H ₂和HD的横截面数据表明，直接的无键跃迁也有助于电子诱导的解吸。