Suite of Standards for Electromagnetic Material Characterization Using Mode Matching Theory

The objective of this research is to determine if an acceptable standard can be developed to access the accuracy and precision of measurements taken using waveguide systems. Tiny changes in material fabrication, processing, and environment can cause problems with accuracy and precision in measurement. There is a great deal of research on uncertainty analysis in the literature. A large portion of the effort will be to determine the levels of uncertainty caused by each of the dimensions of the waveguide insert and to develop a suitable standard capable of verifying system performance. The Mode-Matching Technique will be used to extract input and output S-parameters of a suite of metallic verification waveguide standards. This suite will be used to set a new standard for acceptable tolerances of waveguide systems. After running the theoretical values of Scattering parameters against measured values, it can be determined whether small changes to the parameters of uncertainty greatly affect the measurements. If these changes only cause small changes in measurement, this will be considered an effective standard

Nitrogen K-shell photoabsorption

Reliable atomic data have been computed for the spectral modeling of the nitrogen K lines, which may lead to useful astrophysical diagnostics. Data sets comprise valence and K-vacancy level energies, wavelengths, Einstein $A$-coefficients, radiative and Auger widths and K-edge photoionization cross sections. An important issue is the lack of measurements which are usually employed to fine-tune calculations so as to attain spectroscopic accuracy. In order to estimate data quality, several atomic structure codes are used and extensive comparisons with previous theoretical data have been carried out. In the calculation of K photoabsorption with the Breit--Pauli $R$-matrix method, both radiation and Auger damping, which cause the smearing of the K edge, are taken into account. This work is part of a wider project to compute atomic data in the X-ray regime to be included in the database of the popular {\sc xstar} modeling code

Advances in Atomic Data for Neutron-Capture Elements

Neutron(n)-capture elements (atomic number Z>30), which can be produced in planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements. However, significant challenges must be addressed before this goal can be achieved. One of the most substantial hurdles is the lack of atomic data for n-capture elements, particularly that needed to solve for their ionization equilibrium (and hence to convert ionic abundances to elemental abundances). To address this need, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr. The calculations were benchmarked against experimental photoionization cross section measurements. In addition, we computed charge transfer (CT) rate coefficients for ions of six n-capture elements. These efforts will enable the accurate determination of nebular Se and Kr abundances, allowing robust investigations of s-process enrichments in PNe.Comment: To be published in IAU Symp. 283: Planetary Nebulae, an Eye to the Future; 2 page

Radiative and Auger decay data for modelling nickel K lines

Radiative and Auger decay data have been calculated for modelling the K lines in ions of the nickel isonuclear sequence, from Ni$^+$ up to Ni$^{27+}$. Level energies, transition wavelengths, radiative transition probabilities, and radiative and Auger widths have been determined using Cowan's Hartree--Fock with Relativistic corrections (HFR) method. Auger widths for the third-row ions (Ni$^+$--Ni$^{10+}$) have been computed using single-configuration average (SCA) compact formulae. Results are compared with data sets computed with the AUTOSTRUCTURE and MCDF atomic structure codes and with available experimental and theoretical values, mainly in highly ionized ions and in the solid state.Comment: submitted to ApJS. 42 pages. 12 figure

Atomic data from the IRON Project. I. Electron-impact scattering of Fe17+ using <I>R</I>-matrix theory with intermediate coupling

We present results for electron-impact excitation of F-like Fe calculated using R-matrix theory where an intermediate-coupling frame transformation (ICFT) is used to obtain level-resolved collision strengths. Two such calculations are performed, the first expands the target using 2s2 2p5, 2s 2p6, 2s2 2p4 3l, 2s 2p5 3l, and 2p6 3l configurations while the second calculation includes the 2s2 2p4 4l, 2s 2p5 4l, and 2p6 4l configurations as well. The effect of the additional structure in the latter calculation on the n=3 resonances is explored and compared with previous calculations. We find strong resonant enhancement of the effective collision strengths to the 2s2 2p4 3s levels. A comparison with a Chandra X-ray observation of Capella shows that the n=4 R-matrix calculation leads to good agreement with observation</p

K-shell photoionization of Na-like to Cl)like ions of Mg, Si, S, Ar and Ca

peer reviewe

K-shell photoionization of Nickel ions using R-matrix

We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of the Li-like to Ca-like ions stages of Ni. Level-resolved, Breit-Pauli calculations were performed for the Li-like to Na-like stages. Term-resolved calculations, which include the mass-velocity and Darwin relativistic corrections, were performed for the Mg-like to Ca-like ion stages. This data set is extended up to Fe-like Ni using the distorted wave approximation as implemented by AUTOSTRUCTURE. The R-matrix calculations include the effects of radiative and Auger dampings by means of an optical potential. The damping processes affect the absorption resonances converging to the K thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the K-shell photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.Comment: 23 pages, 6 figures. Accepted in ApJS

Modeling the Oxygen K Absorption in the Interstellar Medium: An XMM-Newton View of Sco X-1

We investigate the absorption structure of the oxygen in the interstellar medium by analyzing XMM-Newton observations of the low mass X-ray binary Sco X-1. We use simple models based on the O I atomic cross section from different sources to fit the data and evaluate the impact of the atomic data in the interpretation of astrophysical observations. We show that relatively small differences in the atomic calculations can yield spurious results. We also show that the most complete and accurate set of atomic cross sections successfully reproduce the observed data in the 21 - 24.5 Angstrom wavelength region of the spectrum. Our fits indicate that the absorption is mainly due to neutral gas with an ionization parameter of Epsilon = 10(exp -4) erg/sq cm, and an oxygen column density of N(sub O) approx. = 8-10 x 10(exp 17)/sq cm. Our models are able to reproduce both the K edge and the K(alpha) absorption line from O I, which are the two main features in this region. We find no conclusive evidence for absorption by other than atomic oxygen

Heasim and Skyback Simulation Tools and Their Application to the Hitomi Mission

We present an introduction to the heasim multimission observation and skyback background, high-energy pseudo Monte Carlo astrophysical simulation tools. Heasim may be used to accurately and efficiently construct flexible image transport system (FITS) event files for simple or composite sources with a wide range of standard and user-defined spatial, spectral, and temporal characteristics. Skyback is designed to enable users to assess the impact of background discrete and diffuse emission on prospective observations, and skyback output may be directly input into heasim. We present a brief overview of heasim and skyback input, algorithms, usage, and output. We also introduce the sxsbranch tool that computes Hitomi soft X-ray spectrometer resolution grade branching ratios, emphasizing its application to simulations. We include several examples of particular relevance to the Hitomi mission