A relationship between electron transfer rates and molecular conduction

This note discusses the relationship between a given intramolecular bridge assisted electron transfer rate and the corresponding zero bias molecular conduction of the same molecular species.Comment: 7 pages. Journal Physical Chemistry, in pres

Low-temperature thermionic emitter Final report, 9 Feb. 1969 - 9 Apr. 1970

Fabrication processes for integrated vacuum circuits and life tests of dual triodes for low temperature thermionic emitter

Charge Transport in Polymer Ion Conductors: a Monte Carlo Study

Diffusion of ions through a fluctuating polymeric host is studied both by Monte Carlo simulation of the complete system dynamics and by dynamic bond percolation (DBP) theory. Comparison of both methods suggests a multiscale-like approach for calculating the diffusion coefficients of the ion

Raman scattering in current carrying molecular junctions. A preliminary account

This is a preliminary acount of a theory for Raman scattering by current-carrying molecular junctions. The approach combines a non-equilibrium Green's function (NEGF) description of the non-equilibrium junction with a generalized scattering theory formulation for evaluating the light scattering signal. This generalizes our previous study (Phys. Rev. Lett. 95, 206802 (2005); J. Chem. Phys. 124, 234709 (2006)) of junction spectroscopy by including molecular vibrations and developing machinery for calculation of state-to-state (Raman scattering) fluxes within the NEGF formalism. For large enough voltage bias we find that the light scattering signal contains, in addition to the normal signal associated with the molecular ground electronic state, also a contribution from the inverse process originated from the excited molecular state as well as an interference component. The effect of coupling to the electrodes and of the imposed bias on the total Raman scattering as well as its components are discussed. Our result reduces to the standard expression for Raman scattering in the isolated molecule case, i.e. in the absence of coupling to the electrodes. The theory is used to discuss the charge transfer contribution to surface enhanced Raman scattering for molecules adsorbed on metal surfaces and its manifestation in the biased junction.Comment: 46 pages, 7 figure

Born Oppenheimer Dynamics Near Metal Surfaces

We discuss the usefulness of Born-Oppenheimer potential surfaces for nuclear dynamics for molecules strongly coupled to metal surfaces. A simple model demonstrating the construction of such surface for a molecular junction is discussed.Comment: 5 pages, 2 figure

On optical spectroscopy of molecular junctions

We compare theoretical techniques utilized for description of optical response in molecular junctions, and their application to simulate Raman spectroscopy in such systems. Strong and weak sides of the Hilbert vs. Liouville space, as well as quasiparticles vs. many-body states, formulations are discussed. Common origins of the methodologies and different approximations utilized in different formulations are identified.Comment: 17 pages, 4 figure

Theory of light-induced current in molecular-tunneling junctions excited with intense shaped pulses

A theory for light-induced current by strong optical pulses in molecular-tunneling junctions is described. We consider a molecular bridge represented by its highest occupied and lowest unoccupied levels, HOMO and LUMO, respectively. We take into account two types of couplings between the molecule and the metal leads: electron transfer that gives rise to net current in the biased junction and energy transfer between the molecule and electron-hole excitations in the leads. Using a Markovian approximation, we derive a closed system of equations for the expectation values of the relevant variables: populations and molecular polarization that are binary, and exciton populations that are tetradic in the annihilation and creation operators for electrons in the molecular states. We have proposed an optical control method using chirped pulses for enhancing charge transfer in unbiased junctions where the bridging molecule is characterized by a strong charge-transfer transition. An approximate analytical solution of the resulting dynamical equation is supported by a full numerical solution. When energy transfer between the molecule and electron-hole excitations in the leads is absent, the optical control problem for inducing charge transfer with linearly chirped pulse can be reduced to the Landau-Zener transition to a decaying level. When chirp is fast with respect to the rate of the electron transfer, the Landau theory is recovered. The proposed control mechanism is potentially useful for developing novel opto-electronic single-electron devices with optical gating based on molecular nanojunctions.Comment: 14 pages, 7 figures; submitted to PR