P. Mandelbaum

Bio: P. Mandelbaum is an academic researcher from Jerusalem College of Engineering, Chennai. The author has contributed to research in topics: Ionization & Spectral line. The author has an hindex of 21, co-authored 70 publications receiving 1428 citations. Previous affiliations of P. Mandelbaum include Humboldt University of Berlin & Hebrew University of Jerusalem.

The potential for plasma diagnostics from stellar extreme-ultraviolet observations

Abstract: A description of the lines from the most abundant ions in the EUV spectrum in the range 50-500 A that have special diagnostic significance is presented. These lines are from plasmas in the temperature range from 10 exp 5 to 10 exp 7 K. Their utility for determining temperature, density, and abundances is demonstrated. An objective grating spectrometer, based on the Skylab slitless spectrograph, for making celestial observations in the EUV spectral region with high spectral resolution is also described. Such an instrument, if equipped with a multilayer grating, can achieve efficiencies over limited EUV wavelength ranges that rival much larger telescope-spectrometer instruments for the observation of stars and other celestial objects.

Line and Band Emission from Tungsten Ions with Charge 21+ to 45+ in the 45-79 Å Range

Abstract: We have measured the radiation from medium-charge-state ions of tungsten in the spectral range from 45 to 70 \AA{}. The ions were produced in an electron beam ion trap (EBIT), and the radiation was observed using a 2-m grazing-incidence spectrometer. Operating EBIT with beam energies between 500 eV and 4 keV allowed us to sample charge states ranging from I-like ${\mathrm{W}}^{21+}$ to Cu-like ${\mathrm{W}}^{45+}.$ Lines of Sr-like through Cu-like tungsten were observed; for the Sr-like to As-like ions new lines were identified. Analysis of the spectra is based on ab initio calculations using the relativistic HULLAC code. For charge states lower than Sr-like ${W}^{36+},$ the spectrum lines fuse into a bright emission band situated around $50 \mathrm{\AA{}}.$ The band extends over an interval of approximately $2 \mathrm{\AA{}}\mathrm{}$ and moves smoothly towards shorter wavelengths with decreasing ion-charge state. The shift and narrowing of the band emission cannot be interpreted in the framework of the standard unresolved transition array formalism assuming statistical population of the excited levels. Instead, the observations are explained by detailed calculations based on a collisional-radiative model. It is shown that the variation of the experimental spectrum with charge state is the signature of the low electron density in EBIT.

Interpretation of the quasicontinuum band emitted by highly ionized rare-earth elements in the 70-100-Å range.

Abstract: Narrow (\ensuremath{\Delta}\ensuremath{\lambda}5 \AA{}), intense quasicontinuum bands, appearing in emission spectra of highly ionized rare-earth elements between 70 and 100 \AA{}, previously observed in tokamaks and laser-produced plasmas, have been obtained from a low-inductance vacuum spark. The bands shift toward shorter wavelengths with increasing atomic number Z. Using the unresolved transition array model, these bands are identified as primarily 4d-4f transitions in Rh i to Rb i--like ions, although the widths come out too large and the mean wavelengths are much too dependent on ionization stages. Detailed ab initio computations show that the interactions between the 4${p}^{6}$4${d}^{N\mathrm{\ensuremath{-}}1}$4f and 4${p}^{5}$4${d}^{N+1}$ configurations are responsible for the narrowing and the superposition of the transition arrays for the different ionization stages of a given element, in agreement with experimental data.

Quenching of transition arrays through configuration mixing

Abstract: In the atomic central-field model, the cancellation of some electric-dipole line strengths is a well known effect of configuration mixings. The authors study their global effects on transition arrays. A crucial quantity is the wavenumber mu 1 of the centre of gravity of two transition arrays when their upper or lower configurations mix. A closed formula is derived for the difference delta Emix between the values of mu 1 with and without the mixing effects. Two experimental examples are presented. In the first one, the value of delta Emix is a sufficient proof that one of the two arrays is almost completely quenched by the other. In the second one, the quenching is only partial, and the degree of quenching is evaluated. In conclusion using the unresolved transition array (UTA) formalism, it is possible to determine ab initio the centre of gravity of a mixed array, without any need for diagonalisation, and to deduce the main effects of configuration mixing.

The flexible atomic code

Abstract: We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...

Chianti—an atomic database for emission lines. xiii. soft x-ray improvements and other changes

Abstract: The CHIANTI spectral code consists of two parts: an atomic database and a suite of computer programs in Python and IDL. Together, they allow the calculation of the optically thin spectrum of astrophysical objects and provide spectroscopic plasma diagnostics for the analysis of astrophysical spectra. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, ionization, and recombination rate coefficients, as well as data to calculate free-free, free-bound, and two-photon continuum emission. Version 7.1 has been released, which includes improved data for several ions, recombination rates, and element abundances. In particular, it provides a large expansion of the CHIANTI models for key Fe ions from Fe VIII to Fe XIV to improve the predicted emission in the 50-170 A wavelength range. All data and programs are freely available at http://www.chiantidatabase.org and in SolarSoft, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net.

CHIANTI - an atomic database for emission lines. IX. Ionization rates, recombination rates, ionization equilibria for the elements hydrogen through zinc and updated atomic data

Abstract: Aims. The goal of the CHIANTI atomic database is to provide a set of atomic data for the interpretation of astrophysical spectra emitted by collisionally dominated, high temperature, optically thin sources. Methods. A complete set of ground level ionization and recombination rate coefficients has been assembled for all atoms and ions of the elements of H through Zn and inserted into the latest version of the CHIANTI database, CHIANTI 6. Ionization rate coefficients are taken from the recent work of Dere (2007, A&A, 466, 771) and recombination rates from a variety of sources in the literature. These new rate coefficients have allowed the calculation of a new set of ionization equilibria and radiative loss rate coefficients. For some ions, such as Fe viii and Fe ix, there are significant differences from previous calculations. In addition, existing atomic parameters have been revised and new atomic parameters inserted into the database. Results. For each ion in the CHIANTI database, elemental abundances, ionization potentials, atomic energy levels, radiative rates, electron and proton collisional rate coefficients, ionization and recombination rate coefficients, and collisional ionization equilibrium populations are provided. In addition, parameters for the calculation of the continuum due to bremsstrahlung, radiative recombination and two-photon decay are provided. A suite of programs written in the Interactive Data Language (IDL) are available to calculate line and continuum emissivities and other properties. All data and programs are freely available at http://wwwsolar.nrl.navy.mil/ chianti

SDO/AIA response to coronal hole, quiet Sun, active region, and flare plasma

Abstract: Aims. We examine the contribution of spectral lines and continuum emission to the EUV channels of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) in different regions of the solar atmosphere. Methods. Synthetic spectra were obtained using the CHIANTI atomic database and sample differential emission measures for coronal hole, quiet Sun, active region and flare plasma. These synthetic spectra were convolved with the effective area of each channel, in order to determine the dominant contribution in different regions of the solar atmosphere. Results. We highlight the contribution of particular spectral lines which under certain conditions can affect the interpretation of SDO/AIA data.

HULLAC, an integrated computer package for atomic processes in plasmas

Abstract: We describe H ULLAC , an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes. This code evolved and has been used over the years, but so far, there was no coherent, comprehensive, and in-depth presentation of it. It is based on relativistic quantum mechanical calculations including configuration interaction. The collisional cross sections are calculated in the distorted wave approximation. The theory and code are presented, emphasizing the various novel methods that has been developed to obtain accurate results very efficiently. In particular we describe the parametric potential method used for both bound and free orbitals, the factorization–interpolation method applied in the derivation of collisional rates, the phase amplitude approach for calculating the continuum orbitals and the N JGRAF graphical method used in the calculation of the angular momentum part of the matrix elements. Special effort has been made to insure the simplicity of use, which is demonstrated in an example.