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

电子摩擦是一种近似处理金属表面原子和分子非绝热动力学的理论概念。我们在这里考虑的非绝热效应是由于违反了博恩-奥本海默近似，由吸附物模式与金属激发连续体的耦合引起的。由非绝热性引发的物理现象，这已经被认为是在这个项目中，除其他外，是：（一）振动激发的吸附物的振动弛豫和与之相关的，在振动光谱线加宽。(ii)反应性与非反应性分子表面散射过程中的能量传递及其影响。(iii)超短激光脉冲激发后表面的基底介导的飞秒化学。这些现象对于光谱学、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，“电子摩擦分子动力学”（MDEF）方法，其中受摩擦力和波动力影响的经典运动方程将进一步发展，并应用于选定的气体表面动力学实例。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，以及两个随时间变化的温度浴的处理（一个用于电子，一个用于声子）在“飞行”AIMDEF中（“Ab Initio MDEF”）模拟。应用涉及与当前实验相关的非平凡示例：（i）系统研究表面不同原子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对吸附位点、金属类型和表面结构的依赖性。(ii)应研究吸附在“裸露”和氢钝化钌表面上的碳氢化合物的受抑平移模式的振动弛豫和振动谱线增宽。(iii)所提出的表面光反应的“动态促进”现象将以激光诱导的氢和氘从Ru（0001）表面的缔合解吸为例进行研究。(iv)最后，我们的目标是更深入地了解在Ru（0001）上CO的激光驱动飞秒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.