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Electron-impact single- and double-ionization cross sections and Maxwellian rate coefficients are presented for the carbon atom. Scaling factors are introduced for the electron-impact excitation and ionization cross sections obtained in the distorted wave (DW) approximation. It is shown that the scaled DW cross sections provide good agreement with measurements for the single ionization of the C atom and C1+ ion. The direct double-ionization (DDI) process is studied using a multi-step approach. Ionization–ionization, excitation–ionization–ionization, and ionization–excitation–ionization branches are analyzed. It is demonstrated that the three-step processes contribute ≼40% of the total DDI cross sections for the case where one of the electrons takes all of the excess energy after the first ionization process. [ABSTRACT FROM AUTHOR]

The momentum distribution of 11 Be fragments produced by the breakup of 12 Be interacting with a proton target at 700.5 MeV/ u energy has been measured at GSI Darmstadt. To obtain the structure information on the anomaly of the N = 8 neutron shell, the momentum distribution of 11 Be fragments from the one-neutron knockout Be 12 ( p , p n ) reaction, measured in inverse kinematics, has been analysed in the distorted wave impulse approximation (DWIA) based on a quasi-free scattering scenario. The DWIA analysis shows a surprisingly strong contribution of the neutron 0 d 5 / 2 orbital in 12 Be to the transverse momentum distribution of the 11 Be fragments. The single-neutron 0 d 5 / 2 spectroscopic factor deduced from the present knock-out data is 1.39(10), which is significantly larger than that deduced recently from data of 12 Be breakup on a carbon target. This result provides a strong experimental evidence for the dominance of the neutron ν ( 0 d 5 / 2 ) 2 configuration in the ground state of 12 Be. [ABSTRACT FROM AUTHOR]

Collision strengths for all 1326 transitions among lowest 52 fine-structure levels of Br XXVII have been computed using Dirac atomic R-matrix code (DARC). Resonances in the threshold region have been completely resolved and the contributions of these resonances to allowed and forbidden transitions have been presented. The partial collision strength for each angular momentum has been studied graphically. Effective collision strengths have also been determined within the temperature range for all 1326 transitions among the lowest 52 levels. Target state energies of the lowest 52 fine-structure levels have been computed from the multi-configuration Dirac-Fock method (MCDF). Additionally, similar calculations with the relativistic distorted wave method and flexible atomic code (FAC) have also been performed to check the accuracy of our results. The present work represents a new and significant work with improvement in the field. We believe that our presented data of collision and effective collision strengths may be useful in the future for benchmark calculations and for plasma diagnostics. [ABSTRACT FROM AUTHOR]

Recent data on the differential angular distribution for the transfer reaction 11 Li( p , d ) 10 Li at E / A = 5.7 MeV in inverse kinematics are analyzed within the DWBA reaction framework, using the overlap functions calculated within a three-body model of 11 Li. The weight of the different 10 Li configurations in the system's ground state is obtained from the structure calculations unambiguously. The effect of the 9 Li spin in the calculated observables is also investigated. We find that, although all the considered models succeed in reproducing the shape of the data, the magnitude is very sensitive to the content of p 1 / 2 wave in the 11 Li ground-state wave function. Among the considered models, the best agreement with the data is obtained when the 11 Li ground state contains a ∼31% of p 1 / 2 wave in the n – 9 Li subsystem. Although this model takes into account explicitly the splitting of the 1 + and 2 + resonances due to the coupling of the p 1 / 2 wave to the 3 / 2 − spin of the core, a similar degree of agreement can be achieved with a model in which the 9 Li spin is ignored, provided that it contains a similar p -wave content. [ABSTRACT FROM AUTHOR]

A novel microwave imaging approach to reconstruct the dielectric properties of targets hosted in partially known, noncanonical, scenarios is proposed and assessed. The method takes joint advantage of the recently introduced virtual experiments paradigm and exploits a new linear approximation developed within such a framework. Such an approximation implicitly depends on the unknown targets and, therefore, has a broader applicability as compared with the traditional distorted Born approximation. Being noniterative, the resulting distorted-wave inversion method is capable of quasi-real-time imaging and successfully images nonweak perturbations. The performances of the novel imaging method have been assessed with simulated data and validated experimentally against some of Fresnel data sets. [ABSTRACT FROM PUBLISHER]

Full finite-range (FFR) distorted-wave Born approximation (DWBA) method has been applied to analyse the angular distributions of cross-sections of the Ca(Li, d) Ti reaction at 28 MeV incident energy for the 22 transitions involving both the bound and unbound states of Ti by using the normal optical, Michel and molecular potentials. The extracted spectroscopic factors for the three optical potentials are compared with those of some previous studies of zero-range (ZR) calculations of the Ca(Li, d) Ti reaction using the normal optical potential. The χ values of all the levels are obtained for the three optical potentials to estimate the quality of the fits. Molecular and Michel potentials have been used for the first time to analyse the four-nucleon transfer reaction and it seems that the molecular potential fits the experimental data more satisfactorily for some of the states than the normal optical and Michel potentials. [ABSTRACT FROM AUTHOR]

We investigate the source of the discrepancy between R-matrix and distorted-wave (DW) collision strengths for J-J' = 0-0 transitions in Mg-like ions, for example 3s2 1S0-3p2 1S0, as reported previously. We find it to be due to the neglect of coupling, for example via 3s3p 1P1, as done by most DW codes. We have implemented an option to account for such coupling as a perturbation within the autostructure DW code. This removes the discrepancy of a factor ~10 and ~100 for Fe14+ and S4+, respectively, for such transitions. The neglect of coupling would have affected (to some degree) the atomic data for a few weak optically forbidden transitions in other isoelectronic sequences if they were calculated with DWcodes such as FAC and HULLAC. In addition, we compare the Fe14+ line intensities predicted with the R-matrix collision strengths against observations of solar active regions and flares; they agree well. For Fe14+, we suggest that the best density diagnostic ratio is 327.0/321.8 Å. [ABSTRACT FROM AUTHOR]

The relativistic R-matrix method is used to calculate the total photoionization cross sections from the ground state 1s22s2 1S0 of Al X for photon energies ranges from the first ionization threshold to just above the eighth threshold of the residual ion Al XI. In this work, the relativistic distorted-wave method is employed to calculate the fine-structure energy levels and radial functions. The lowest eight level target states of Al XI are used in the photoionization calculations of Al X and should provide a reasonably complete database for practical application for photoionization cross section for Al X. The resonance energy levels and widths of 18 Rydberg series have been investigated. [ABSTRACT FROM AUTHOR]

An analysis is presented of measured and calculated cross sections for inner-shell ionization by electron impact. We describe the essentials of classical and semiclassical models and of quantum approximations for computing ionization cross sections. The emphasis is on the recent formulation of the distorted-wave Born approximation by Bote and Salvat [Phys. Rev. A 77, 042701 (2008)] that has been used to generate an extensive database of cross sections for the ionization of the K shell and the L and M subshells of all elements from hydrogen to einsteinium (Z = 1 to Z = 99) by electrons and positrons with kinetic energies up to 1 GeV.We describe a systematic method for evaluating cross sections for emission of x rays and Auger electrons based on atomic transition probabilities from the Evaluated Atomic Data Library of Perkins et al. [Lawrence Livermore National Laboratory, UCRL-ID-50400, 1991]. We made an extensive comparison of measured K-shell, L-subshell, and M-subshell ionization cross sections and of Lα x-ray production cross sections with the corresponding calculated cross sections. We identified elements for which there were at least three (for K shells) or two (for L and M subshells) mutually consistent sets of cross-section measurements and for which the cross sections varied with energy as expected by theory. The overall average root-mean-square deviation between the measured and calculated cross sections was 10.9% and the overall average deviation was -2.5%. This degree of agreement between measured and calculated ionization and x-ray production cross sections was considered to be very satisfactory given the difficulties of these measurements. [ABSTRACT FROM AUTHOR]

A correction to the article "An R Package for Modelling the Scattering Properties of Weak Scattering Targets Using the Distorted Wave Born Approximation" by Sven Gastauer et al is presented.

The next-generation Ethernet passive optical network (NG-EPON) is basically classified into two architectures on the basis of the wavelength sharing by the optical network units (ONUs). The single scheduling domain (SSD) and multi-scheduling domain (MSD) EPON are the two different design architectures for NG-EPON. A vital task in NG-EPON is to design dynamic wavelength bandwidth allocation (DWBA) algorithms that can meet the future demands of the network subscribers. A number of DWBA algorithms have been designed for time and wavelength division multiplex (TWDM) EPON. The existing DWBA algorithms for TWDM-EPON could be used in MSD-EPON by making necessary parametric changes. The design and implementation of new DWBA algorithms for MSD-EPON are still required specifically. In this paper, we have proposed a quality of service (QoS)-based DWBA algorithm for NG-EPON. We have comparatively analyzed our proposed DWBA with the existing algorithms like earlier finished time (EFT), weighted bipartite matching (WBM), and earlier finished time with void filling (EFT-VF). The results show that our proposed DWBA algorithm performs better as compared to EFT, WBM, and EFT-VF on the basis of average packet delay and average completion time for NG-EPON. [ABSTRACT FROM AUTHOR]

This paper studies how limited information in data acquired by a wideband microwave tomography (MWT) system can affect the quality of reconstructed images. Limitations can arise from experimental errors, mismatch between the system and its model in the imaging algorithm, or losses in the immersion and coupling medium which are required to moderate this mismatch. We also present a strategy for improving reconstruction performance by discarding data that is dominated by experimental errors. The approach relies on recording transmitted signals in a wide frequency range, and then correlating the data in different frequencies. We apply this method to our wideband MWT prototype, which has been developed in our previous work. Using this system, we present results from simulated and experimental data which demonstrate the practical value of the frequency selection approach. We also propose a K-neighbour method to identify low quality data in a robust manner. The resulting enhancement in imaging quality suggests that this approach can be useful for various medical imaging scenarios, provided that data from multiple frequencies can be acquired and used in the reconstruction process. [ABSTRACT FROM AUTHOR]

Differential cross sections and spin asymmetries for the elastic scattering of spin-polarized electrons from inert spin- nuclei are calculated within the distorted-wave (DW) Born approximation. This is achieved by means of a coherent superposition of the electric and magnetic (M1) transition amplitudes, using Dirac eigenfunctions for the electronic scattering states throughout. For heavy nuclei (Z ≳ 40), high collision energies and backward scattering angles considerable deviations occur from previous DW plane-wave calculations where the magnetic transition is calculated within the Born approximation. For electrons spin-polarized perpendicular to the beam direction the spin asymmetry is quenched when magnetic scattering becomes dominant. Predictions are made for 50–200 MeV electrons scattering from 15N, 89Y and 207Pb nuclei. [ABSTRACT FROM AUTHOR]