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Full-Text Articles in Physics

Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton Jun 1997

Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton

All HMC Faculty Publications and Research

Two independent methods are presented for the nonperturbative calculation of the electronic coupling matrix element (Hab) for electron transfer reactions using ab initio electronic structure theory. The first is based on the generalized Mulliken–Hush (GMH) model, a multistate generalization of the Mulliken Hush formalism for the electronic coupling. The second is based on the block diagonalization (BD) approach of Cederbaum, Domcke, and co-workers. Detailed quantitative comparisons of the two methods are carried out based on results for (a) several states of the system Zn2OH2+ and (b) the low-lying states of the benzene–Cl atom complex and its contact ion pair. Generally …


Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, M. Murphy, C. Glasheen, F. A. Moscatelli, Thomas D. Donnelly Apr 1997

Optimization Of Plasmas For Recombination-Pumped Short-Wavelength Lasers, M. Murphy, C. Glasheen, F. A. Moscatelli, Thomas D. Donnelly

All HMC Faculty Publications and Research

We report on experiments investigating the optimization of laser-ablated plasmas which are used to produce recombination-pumped, short-wavelength lasers. We evaluate the density of electrons and neutral atoms in laser ablated lithium and carbon plasmas as a function of time and distance away from the ablated target surface. We use an interferometric technique which can reveal information about the temperature of the plasma electrons. We find that the cold electrons which result in gain in recombination-pumped lithium lasers on the Lyman-α transition are produced by the high-intensity pump pulse rather than the lower intensity ablating pulse.


Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher Feb 1997

Photoluminescence Properties Of Silicon Quantum-Well Layers, Peter N. Saeta, A. C. Gallagher

All HMC Faculty Publications and Research

Nanometer-scale crystal silicon films surrounded by SiO2 were prepared by oxidizing silicon-on-insulator substrates prepared from SIMOX (separation by implantation of oxygen) and crystallized hydrogenated amorphous silicon films. Average silicon layer thickness was determined from reflection spectra. When sufficiently thin (<2 >nm), all layers emitted red photoluminescence under blue and UV cw excitation, with a spectrum that did not depend on the mean layer thickness. The spectrum was roughly Gaussian with a peak energy of 1.65 eV, which is lower than for most porous silicon spectra. The time scale for the luminescence decay was ~35 μs at room temperature and …


The Interaction Of A Point Vortex With A Wall-Bounded Vortex Layer, Oliver V. Atassi, Andrew J. Bernoff, Seth Lichter Jan 1997

The Interaction Of A Point Vortex With A Wall-Bounded Vortex Layer, Oliver V. Atassi, Andrew J. Bernoff, Seth Lichter

All HMC Faculty Publications and Research

The interaction of a point vortex with a layer of constant vorticity, bounded below by a wall and above by an irrotational flow, is investigated as a model of vortex–boundary layer interaction. This model calculates both the evolution of the interface which separates the vortex layer from the irrotational flow and the trajectory of the vortex. In order to determine the conditions which lead to sustained unsteady interaction, three cases are investigated where the mutual interaction between the vortex and interface is initially assumed to be weak. (i) When a weak point vortex lies outside the layer, the vortex moves …