Study of attosecond delays using perturbation diagrams and exterior complex scaling

We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange (RPAE). Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M -shell of argon atoms, where experiments have been carried out using the so-called RABITT technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon.Comment: 36 pages, 10 figure

Effects of Aspen Phenolic Glycosides on Gypsy Moth (Lepidoptera: Lymantriidae) Susceptibility to \u3ci\u3eBacillus Thuringiensis\u3c/i\u3e

Performance of the gypsy moth, Lymantria dispar, on quaking aspen, Populus tremuloides, is strongly affected by foliar concentrations of phenolic glycosides. Because the microbial insecticide Bacillus thuringiensis is widely used against gypsy moths and has a mode of action similar to that of phenolic glycosIdes, we investigated the combined effects of the two toxins on gypsy moth larvae. The experimental design was a 2 x 2 factorial: two levels (0, +) of phenolicglycosides for each of two levels (0, +) of B. thuringiensis. The toxins were incorporated into artificial diets and bioassayed against first and fourth instars. Bacillus thuringiensis and phenolic glycosides ne~atively and addi· tively affected larval survival, growth and development tImes. Both agents slightly reduced consumption rates. In addition, B. thuringiensis reduced diet digestibility whereas phenolic glycosides decreased the efficiency with which food was converted to biomass. These results suggest that the efficacy of B. thuringiensis applications in aspen forests is likely to be affected by the allelo· chemical composition of foliage

Attosecond delays in laser-assisted photodetachment from closed-shell negative ions

We study laser-assisted photodetachment time delays by attosecond pulse trains from the closed-shell negative ions F- and Cl-. We investigate the separability of the delay into two contributions: (i) the Wigner-like delay associated with one-photon ionization by the attosecond pulse train and (ii) the delay associated with exchange of an additional laser photon in the presence of the potential of the remaining target. Based on the asymptotic form of the wave packet, the latter term is expected to be negligible because the ion is neutralized leading to a vanishing laser-ion interaction with increasing electron-atom separation. While this asymptotic behavior is verified at high photoelectron energies, we also quantify sharp deviations at low photoelectron energies. Further, these low-energy delays are clearly different for the two studied anions indicating a breakdown of the universality of laser-ion induced delays. The fact that the short-range potential can induce a delay of as much as 50 as can have implications for the interpretation of delay measurements also in other systems that lack long-range potential.Comment: 11 pages, 9 figures. Accepted for publication in Phys. Rev. A as a regular article (2017-06-16

A Schr\"{o}dinger equation for relativistic laser-matter interactions

A semi-relativistic formulation of light-matter interaction is derived using the so called propagation gauge and the relativistic mass shift. We show that relativistic effects induced by a super-intense laser field can, to a surprisingly large extent, be accounted for by the Schr{\"o}dinger equation, provided that we replace the rest mass in the propagation gauge Hamiltonian by the corresponding time-dependent field-dressed mass. The validity of the semi-relativistic approach is tested numerically on a hydrogen atom exposed to an intense XUV laser pulse strong enough to accelerate the electron towards relativistic velocities. It is found that while the results obtained from the ordinary (non-relativistic) Schr{\"o}dinger equation generally differ from those of the Dirac equation, merely demonstrating that relativistic effects are significant, the semi-relativistic formulation provides results in quantitative agreement with a fully relativistic treatment

The Multi-Configurational Hartree-Fock close-coupling ansatz: application to Argon photoionization cross section and delays

We present a robust, ab initio method for addressing atom-light interactions and apply it to photoionization of argon. We use a close-coupling ansatz constructed on a multi-configurational Hartree-Fock description of localized states and B-spline expansions of the electron radial wave functions. In this implementation, the general many-electron problem can be tackled thanks to the use of the ATSP2K libraries [CPC 176 (2007) 559]. In the present contribution, we combine this method with exterior complex scaling, thereby allowing for the computation of the complex partial amplitudes that encode the whole dynamics of the photoionization process. The method is validated on the 3s3p6np series of resonances converging to the 3s extraction. Then, it is used for computing the energy dependent differential atomic delay between 3p and 3s photoemission, and agreement is found with the measurements of Gu\'enot et al. [PRA 85 (2012) 053424]. The effect of the presence of resonances in the one-photon spectrum on photoionization delay measurements is studied.Comment: 15 pages, 8 figures, 4 table

Effects of Ascorbic Acid Deficiencies on Larvae of \u3ci\u3eLymantria Dispar\u3c/i\u3e (Lepidoptera: Lymantriidae)

We assessed the effects of ascorbic acid and total vitamin deficiencies on growth, food processing efficiencies and survival of larval gypsy moths. Artificial diet lacking ascorbic acid did not alter performance of fourth instars, whereas diet lacking a total vitamin mix margmally reduced growth. All vita- min deficient diets substantially reduced survival of fourth-fifth instars. Mortality occurred primarily during molting periods. providing further evidence of the putative role of ascorbic acid in cuticle formation

Confinement sensitivity in quantum dot singlet-triplet relaxation

Spin-orbit mediated phonon relaxation in a two-dimensional quantum dot is investigated using different confining potentials. Elliptical harmonic oscillator and cylindrical well results are compared to each other in the case of a two-electron GaAs quantum dot subjected to a tilted magnetic field. The lowest energy set of two-body singlet and triplet states are calculated including spin-orbit and magnetic effects. These are used to calculate the phonon induced transition rate from the excited triplet to the ground state singlet for magnetic fields up to where the states cross. The roll of the cubic Dresselhaus effect and the positioning of "spin hot-spots" are discussed and relaxation rates for a few different systems are exhibited

Toxic Phenolic Glycosides From \u3ci\u3ePopulus:\u3c/i\u3e Physiological Adaptations of the Western North American Tiger Swallowtail Butterfly, \u3ci\u3ePapilio Rutulus\u3c/i\u3e (Lepidoptera: Papilionidae)

The phenolic glycosides tremulacin and salicortin found in quaking aspen, Populus tremuloides, and other members of the Salicaceae, are known to be toxic to larvae of the Eastern tiger swallowtail butterfly, Papilio glaucus, but not to the Canadian tiger swallowtail, P. canadensis. Larvae of the western tiger swallowtail, P. rutulus, were not killed nor were their growth rates suppressed when fed a mixture of tremulacin and salicortin on black cherry leaves. When the Salicaceae adapted P. rutulus penultimate instar larvae were fed a combination of the two phenolic glycosides and the esterase inhibitor (DEF S,S,S-tributylphosphorotrithioate), growth was reduced more than 50OJo compared to controls, and half of the larvae died before completing the instaL Our results indicate that esterase detoxification mechanisms are involved in the western tiger swallowtail, P. rutulus, as is also known to be the case for the northern tiger swallowtail, P. canadensis. It is not known whether the same esterase isozyme is involved in both species. From an evolutionary perspective such information could help resolve whether the Salicaceae-adapted swallowtails species are a monophyletic group (perhaps due to isolation in the Beringial Pleistocene glacial refuge of Alaska)