Recombination Rate Coefficients for KLL Di-electronic Satellite Lines of Fe XXV and Ni XXVII

The unified method for total electron-ion recombination is extended to study the dielectronic satellite (DES) lines. These lines, formed from radiative decay of autoionizing states, are highly sensitive temperature diagnostics of astrophysical and laboratory plasma sources. The computation of the unified recombination rates is based on the relativistic Breit-Pauli R-matrix method and close coupling approximation. Extending the theoretical formulation developed earlier we present recombination rate coefficients for the 22 satellite lines of KLL complexes of helium-like Fe XXV and Ni XXVII. The isolated resonance approximation, commonly used throughout plasma modeling, treats these resonances essentially as bound features except for dielectronic capture into, and autoionization out of, these levels. A line profile or cross section shape is often assumed. On the other hand, by including the coupling between the autoionizing and continuum channels, the unified method gives the intrinsic spectrum of DES lines which includes not only the energies and strengths, but also the natural line or cross section shapes. A formulation is presented to derive autoionization rates from unified resonance strengths and enable correspondence with the isolated resonance approximation. While the rates compare very well with existing rates for the strong lines to <20%, the differences for weaker DES lines are larger. We also illustrate the application of the present results to the analysis of K ALPHA complexes observed in high-temperature X-ray emission spectra of Fe XXV and Ni XXVII. There are considerable differences with previous results in the total KLL intensity for Fe XXV at temperatures below the temperature of maximum abundance in coronal equilibrium. (Abbreviated Abstract)Comment: 21 pages, 5 figures, to appear in Physica Script

Students as Partners in E-Content Creation: A case study exploring student-staff partnership for learning and student engagement using digital applications for co-creation of e-learning materials.

In order to enable learners to take control of their learning needs and actively contribute in their learning processes, educators can partner with students in various reciprocal student-staff partnership (SSP) settings where students can be co-creators, co-producers, curators or co-deliverers of the curriculum. This case study, undertaken to enhance the curriculum as part of teaching qualification, places emphasis on educators partnering with first-year undergraduate students over e-content creation within an existing module using readily accessible digital applications in order to promote active learning in students and improve student engagement. The extent to which SSP as an approach to the creation of e-learning materials using digital applications, enhanced learning and student engagement in an existing module, was evaluated. Results indicated, students’ perceived SSP to be an excellent platform for learning, actively engaging in the classroom as well as for developing various skills. However, some concerns were expressed with regards to overcoming the power hierarchy barrier within an SSP initiative

Photoionization of the 7d excited state of cesium

Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.htmlThe photoionization cross section for the excited 7d state of atomic cesium has been calculated in the Hartree-Fock approximation. The results show excellent agreement with a recent measurement.This work was supported by the U.S. Army Research Office and the National Science Foundation

Photoelectron angular distribution of the excited 2p^2 3p ^2S state of atomic nitrogen

Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.htmlCalculations of the photoelectron angular distribution asymmetry parameter ß for the excited 2p^2 3p ^2S state of atomic nitrogen have been performed using Hartree-Fock discrete and continuum wave functions with relaxation. The results show reasonably good agreement with a recent measurement of ß at a single energy.The work was supported by the U.S. Army Research Office and the National Science Foundation

On certain subclasses of p-valent functions defined in terms of certain fractional derivative operators

In the present paper we study certain subclasses Hλ,μ,η(a,b,pσ) and Kλ,μ,η(a,b,pσ) of analytic and p-valent functions. The results presented include coefficient estimates and distorsion properties for functions belonging to such classes. Further results giving closure theorems, various properties and modified Hadamard products of several functions belonging to above classes are also mentioned

Chemical Abundances from the Continuum

The calculation of solar absolute fluxes in the near-UV is revisited, discussing in some detail recent updates in theoretical calculations of bound-free opacity from metals. Modest changes in the abundances of elements such as Mg and the iron-peak elements have a significant impact on the atmospheric structure, and therefore self-consistent calculations are necessary. With small adjustments to the solar photospheric composition, we are able to reproduce fairly well the observed solar fluxes between 200 and 270 nm, and between 300 and 420 nm, but find too much absorption in the 270-290 nm window. A comparison between our reference 1D model and a 3D time-dependent hydrodynamical simulation indicates that the continuum flux is only weakly sensitive to 3D effects, with corrections reaching <10% in the near-UV, and <2% in the optical.Comment: 10 pages, 5 figures, to appear in the proceedings of the conference A Stellar Journey, a symposium in celebration of Bengt Gustafsson's 65th birthday, June 23-27, 2008, Uppsal