David A. Micha

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Starting from the atomic structure of silicon quantum dots (QDs), and utilizing ab initio electronic structure calculations within the Förster resonance energy transfer (FRET) treatment, a model has been developed to characterize electronic excitation energy transfer between QDs. Electronic energy transfer rates, KEET, between selected identical pairs of(More)
The interaction of an excited adsorbate with a medium undergoing electronic and vibrational transitions leads to fast dissipation due to electronic energy relaxation and slow (or delayed) dissipation from vibrational energy relaxation. A theoretical and computational treatment of these phenomena has been done in terms of a reduced density matrix satisfying(More)
We treat electronic dynamics at surfaces of nanostructured semiconductors induced by absorption of visible light using reduced density matrices and properties obtained from ab initio electronic structure calculations, to focus on two non-adiabatic phenomena: (a) how active electrons interacting non-adiabatically with atoms at the surface undergo electronic(More)
A new general computational procedure is presented to obtain photoconductivities starting from atomic structures, combining ab initio electronic energy band states with populations from density matrix theory, and implemented for a specific set of materials based on Si crystalline slabs and their nanostructured surfaces without and with adsorbed Ag clusters.(More)
A mixed quantum-classical formulation is developed for a quantum subsystem in strong interaction with an N-particle environment, to be treated as classical in the framework of a hydrodynamic representation. Starting from the quantum Liouville equation for the N-particle distribution and the corresponding reduced single-particle distribution, exact quantum(More)
The dynamics of atoms or molecules adsorbed on a metal surface, and excited by collisions with an atomic beam, are treated within a theory that includes energy dissipation into lattice vibrations by means of a frequency and temperature dependent friction function. The theory provides dynamic structure factors for energy transfer derived from collisional(More)
The optical properties of Si quantum dots (QDs) with phosphorous and aluminum dopants have been calculated with the recently tested Heyd-Scuseria-Ernzerhof (HSE) density functionals to ascertain the effect of functional corrections to electronic self-interaction. New results have been obtained for 20 crystalline and amorphous structures of Si(29) and Si(35)(More)
We consider two pathways of electron transfer induced by a light pulse between a metal cluster and a semiconductor surface. In direct excitation the pulse excites the system directly to the final (electron transferred) state. In indirect excitation the pulse first photoexcites the system to an intermediate state, which then undergoes nonadiabatic(More)