Density functional theory of the electrical conductivity of molecular devices

Time-dependent density functional theory is extended to include dissipative systems evolving under a master equation, providing a Hamiltonian treatment for molecular electronics. For weak electric fields, the isothermal conductivity is shown to match the adiabatic conductivity, thereby recovering the Landauer result.     

High energy gain of trapped electrons in a tapered, diffraction-dominated inverse-free-electron laser

Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-free-electron-laser (IFEL) accelerator experiment. A 14.5 MeV electron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, approximately 1.8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.     

Coherent analysis of quantum optical sideband modes

We demonstrate a device that allows for the coherent analysis of a pair of optical frequency sidebands in an arbitrary basis. We show that our device is quantum noise limited, and hence applications for this scheme may be found in discrete and continuous variable optical quantum information experiments.     

Efficient photoconductive terahertz source using line excitation

We report significant improvement in terahertz (THz) power and efficiency using photoconductive sources by use of a spatially extended line source excitation and the trap enhanced field effect that occurs in sources made on semi-insulating GaAs. The combination of high electric fields and reduced screening effects allows 10 microW of THz power to be generated with 14 mW of absorbed optical power, demonstrating nearly 0.1% optical-to-THz conversion efficiency.     

The Lanczos phenomenon—An interpretation based upon conjugate gradient optimization

The equivalence in exact arithmetic of the Lanczos tridiagonalization procedure and the conjugate gradient optimization procedure for solving Ax = b, where A is a real symmetric, positive definite matrix, is well known. We demonstrate that a relaxed equivalence is valid in the presence of errors. Specifically we demonstrate that local ε-orthonormality of the Lanczos vectors guarantees local ε-A-conjugacy of the direction vectors in the associated conjugate gradient procedure. Moreover we demonstrate that all the conjugate gradient relationships are satisfied approximately. Therefore, any statements valid for the conjugate gradient optimization procedure, which we show converges under very weak conditions, apply directly to the Lanczos procedure. We then use this equivalence to obtain an explanation of the Lanczos phenomenon: the empirically observed “convergence” of Lanczos eigenvalue procedures despite total loss of the global orthogonality of the Lanczos vectors.     

On homological duality

Duality relations given in terms of natural isomorphisms $\text{Tor}{}^{\mathrm{R}}{}_{\mathrm{n?j}}\text{(D, -)}\text{→}\text{～}\text{Ext}{}^{\mathrm{j}}{}_{\mathrm{R}}\text{(C, -)}$ are shown to be related with a straightforward generalization of the operation of taking the dual Hom_R(P, R) of a finitely generated projective module P. The obtained results allow to characterize duality groups (in the sense of Bieri-Eckmann) and inverse duality groups in a perspicuous way, and to generalize two main result of Matlis [13].     

Guiding center motion of two interacting n=0 Landau electrons in two dimensions

The properties of a two-electron system in two dimensions subjected to a strong magnetic field are considered. Assuming that the electrons are in the lowest Landau level, all observables are expressed in terms of guiding center variables. In these variables, the hamiltonian can be exactly diagonalized.     

Many-particle rapidity correlations in light-ion interactions at the CERN intersecting storage rings

Many-particle rapidity correlations have been studied for αα,dd, andpp interactions at the CERN Intersecting Storage Rings using the Split-Field Magnet detector, and basing the investigating on the distributions of rapidity gaps between particles. In the framework of a simple cluster model, it is found that all the data samples have similar features and that the events contain clusters of two different types.     

Study of 59Cu by means of 58Ni(d,n)

The reaction ⁵⁸Ni(d, n)⁵⁹Cu has been studied at 7.0 MeV bombarding energy. Angular distributions of transitions to 16 states in ⁵⁹Cu have been extracted and analysed with DWBA to yield absolute spectroscopic strengths. The results are compared to those of other measurements.     

A comparison of various methods for calculating unimolecular reaction rate constants

A test of the Kassel quantum expressions for unimolecular rate constants and densities of vibrational states is described. Rate constants are calculated for nine reactions previously used in such tests, over a wide range of temperatures and pressures. The Kassel expression using the geometric mean of the molecular vibration frequencies is generally found to give better results than that using the arithmetic mean.