Quantum Dynamics and Control of Surface Ultra-fast Processes

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Photochemistry on Metal Surfaces: To understand photochemical reactions on surfaces, electronic excitation mechanisms should be specified, and it is well known that the substrate-mediated (indirect) excitation occurs in the majority of reactions on metal surfaces. We have developed a new theoretical method to calculate photon energy dependence of reaction probability triggered by substrate-mediated excitation using Nonequilibrium Green's function (NEGF) theory. We have performed DFT calculations to obtain the dimer adsorption structure and calculated the probability of photodesorption based on our NEGF theory. We have found that while the photoactive species is the NO dimer, a suitable resonant orbital is only one, and this single resonance is enough to reproduce the experimental data.A NEGF approach to interfacial electronic quantum transport: To model electron transport through a molecular junction, we propose an efficient method using an ab initio self-consistent NEGF combined with density functional theory. We have adopted a model close to the extended molecule approach, due to its flexibility, but have improved on the problems relating to molecule-surface couplings and the long-range potential via a systematic procedure for the same ab initio level as that of the Green's function. The resulting algorithm involves three main steps: (i) construction of the embedding potential; (ii) perturbation expansion of the Green's function in the molecular orbital basis; and (iii) truncation of the molecular orbital space by separating it into inactive, active, and virtual spaces. The algorithm is suitable for application to large molecular systems.