Theory of electronic friction of adsorbates at metal surfaces: Methods and applications

电子摩擦是一个理论概念，用来近似处理原子和分子在金属表面的非绝热动力学。我们所考虑的非绝热效应是由于对Born-Oppenheimer近似的破坏，这是由于吸附模式与金属激发的连续体的耦合引起的。由非绝热引发的物理现象，已经在这个项目中被考虑，其中包括：(I)振动激发的吸附的振动弛豫和与之相关的，振动光谱中的谱线加宽。(Ii)反应性和非反应性分子表面散射过程中的能量传递及其影响。(Iii)在超短激光脉冲激发下，表面的衬底介导的飞秒化学。这些现象对光谱学、光化学和金属表面附近的能量传递具有普遍的重要性。在本项目中，将进一步发展受摩擦力和脉动力作用的经典运动方程，并将其应用于选定的气体表面动力学的例子。计划中的方法学发展旨在包括非各向同性修正和表面原子运动对原子、电子摩擦系数的影响，以及在AIMDEF模拟中处理两个随时间变化的温度浴(一个用于电子，一个用于声子)。应用涉及与当前实验相关的非平凡例子：(I)系统地研究不同原子在表面的振动弛豫以及电子和声子弛豫通道所起的作用。我们还希望研究这些现象与吸附位置、金属类型和表面结构的依赖关系。(Ii)应研究吸附在“裸”和氢钝化的Ru表面上的碳氢化合物的受挫平移模式的振动弛豫和振动线加宽。(3)表面光反应的“动态促进”现象应以激光诱导氢和氢从Ru(0001)表面的缔合脱附为例进行研究。(Iv)最后，我们旨在更深入地理解CO在Ru(0001)表面上激光驱动的飞跃化学过程中的动力学细节，以及通过改变激光脉冲参数对其可能的操纵。

Electronic friction is a theoretical concept to treat non-adiabatic dynamics of atoms and molecules at metal surfaces in an approximate way. Non-adiabatic effects we have here in mind are due to the violation of the Born-Oppenheimer approximation, arising from the coupling of adsorbate modes to a continuum of metal excitations. Physical phenomena triggered by non-adiabaticity, which have already been considered in this project, are, among others: (i) The vibrational relaxation of vibrationally excited adsorbates and associated with it, the line broadening in vibrational spectroscopy. (ii) Energy transfer during and influences on, reactive and non-reactive molecule-surface scattering. (iii) Substrate-mediated femtochemistry at surfaces following excitation with ultrashort laser pulses. These phenomena are of general importance for spectroscopy, photochemistry, and energy transfer near metal surfaces.In this project the "Molecular Dynamics with Electronic Friction" (MDEF) method, in which classical equations of motion subject to frictional and fluctuating forces shall be further developed, and applied to selected examples of gas-surface dynamics. Planned methodological developments aim at including non-isotropic corrections and effects of surface atom motion for atomic, electronic friction coefficients, as well as the treatment of two time-dependent temperature baths (one for electrons and one for phonons) in "on the fly" AIMDEF ("Ab Initio MDEF") simulations.Applications concern non-trivial examples which are relevant for current experiments: (i) A systematic study of the vibrational relaxation of different atoms at surfaces and the role played by electronic and phononic relaxation channels. We also wish to study the dependence of these phenomena on the adsorption site, the type of metal, and surface structure. (ii) The vibrational relaxation and vibrational line broadening of frustrated translational modes of hydrocarbons adsorbed on "naked" and hydrogen-passivated, ruthenium surfaces shall be studied. (iii) The proposed phenomenon of "dynamic promotion" of a surface photoreaction shall be investigated for the example of laser-induced associative desorption of hydrogen and deuterium from a Ru(0001) surface. (iv) Finally, we aim at a deeper understanding of dynamical details during laser-driven femtochemistry of CO on Ru(0001), and their possible manipulation by variation of laser pulse parameters.