Threshold effects on angular distributions for multiphoton detachment by intense elliptically polarized light

Unusual threshold effects are found theoretically in the frequency and intensity dependence of angular distributions produced by an elliptically polarized laser as well as in the elliptic dichroism parameter, which measures the asymmetry of the angular distribution.     

Two-photon bremsstrahlung processes in atoms: Polarization effects and analytic results for the Coulomb potential

The partial wave analysis of two-photon free-free (bremsstrahlung) electron transition cross sections during scattering by a static potential U(r), as well as by an atom with a nonzero angular momentum, is carried out. The dipole interaction with radiation is taken into account in the second order of perturbation theory for the general case of elliptic polarization of photons. The polarization and angular dependences of the two-photon potential scattering amplitude is presented as a combination of the scalar product of electron momenta and photon polarization vectors and five atomic parameters containing Legendre polynomials of the scattering angle as well as radial matrix elements depending on the initial (E) and final (E′) electron energies. The results are applicable both for spontaneous double bremsstrahlung at nonrelativistic energies and for induced absorption and emission in the field of a light wave. Specific polarization effects (circular and elliptic dichroism) are analyzed for two-photon bremsstrahlung processes associated with the interference of the Hermite and anti-Hermite parts of the amplitude and depending on the sign of photon helicity. The limiting cases of high and low photon frequencies are investigated analytically, and the asymptotic forms of radial matrix elements and amplitudes for the general form of the U(r) potential are determined. Closed analytic expressions are derived for the radial matrix elements of the Coulomb potential in the form of integrals of hypergeometric function, and singularities are singled out in explicit form for E′ → E. The methods of approximate calculation of the radial matrix elements are discussed, and the results of their exact numerical calculation, as well as angular distributions and the cross sections of induced one-and two-photon emission and absorption, are given for the case of the Coulomb potential. The numerical results show that dichroism effects are quite accessible for experimental observations.     

Elliptic and circular dichroism effects in two-photon double ionization of atoms

An ab initio parametrization of the two-photon double ionization amplitude from an s2 subshell of an atom in a 1S state is presented and used to predict two light polarization effects on photoelectron angular distributions that do not exist in single-photon double ionization: (i) elliptic dichroism and (ii) circular dichroism at equal energy sharing. Estimates for He show large magnitudes for these effects, which provide a means for polarization control of double ionization by vacuum ultraviolet light.     

Models for capacitated lot-sizing problem with backlogging,setup carryover and crossover

Setup operations are significant in some production environments. It is mandatory that their production plans consider some features, as setup state conservation across periods through setup carryover and crossover. The modelling of setup crossover allows more flexible decisions and is essential for problems with long setup times. This paper proposes two models for the capacitated lot-sizing problem with backlogging and setup carryover and crossover. The first is in line with other models from the literature, whereas the second considers a disaggregated setup variable, which tracks the starting and completion times of the setup operation. This innovative approach permits a more compact formulation. Computational results show that the proposed models have outperformed other state-of-the-art formulation.     

Stability and convergence of the spectral Lagrange-Galerkin method for mixed periodic/non-periodic convection-dominated diffusion problems

We present a convergence analysis of the spectral Lagrange-Galerkinmethod for mixed periodic/non-periodic convection-diffusionproblems. The scheme is unconditionally stable, independentof the diffusion coefficient, even in the case when numericalquadrature is used. The theoretical predictions are illustratedby a series of numerical experiments. For the periodic case,our results present a significant improvement on those givenby Süli & Ware (1991) SIAM J. Numer.Anal.28, 423-445).     

Model-independent quantum approach for intense laser detachment of a weakly bound electron

We present a model-independent theory for laser detachment of a weakly bound electron having a nonzero angular momentum. Our treatment reduces to the well-known Keldysh result for tunnel ionization upon neglecting rescattering effects. Numerical results for the above-threshold detachment spectrum of a negative ion having an outer p electron show significant modification of the rescattering plateau as compared to that for an ion having an outer s electron.