Model description of electron transfer between PTCDA molecule and metal surface upon molecular adsorption and STM manipulation

The coupling between the molecule-localized electronic states and continuum of the electronic states of the metal surface is of paramount importance for adsorption dynamics, surface reactivity, as well as for the electron- and photon-induced processes at metal surfaces. Here, using the model one-active-electron description and wave-packet propagation approach, we study the resonant electron transfer between the perylene-tetracarboxylic-dianhydride (PTCDA) molecule and metal substrate from 0.5 nm separations down to the adsorption distances. We also address the situation where the molecule is lifted up from the substrate using the scanning tunneling microscope. A detailed comparison with the large amount of available experimental data and ab initio calculations allows us to discuss the validity of the method and the main robust effects driving the lifetimes of molecule-localized states that it reveals. Thus we show that the symmetry of molecule-localized states strongly impacts the dependence of the electron transfer rates on the metal band structure and molecule-surface distance. In addition, in full agreement with recent experimental data on scanning tunneling microscopy manipulation where an adsorbed molecule is lifted into the vertical geometry, we find an order of magnitude reduction of the adsorbate-substrate coupling.