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M. Arnaud

Bio: M. Arnaud is an academic researcher. The author has contributed to research in topics: Molar ionization energies of the elements & Photoionization. The author has an hindex of 1, co-authored 1 publications receiving 628 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(−25) using the photoionization cross sections of Clark et al.
Abstract: In the past few years important progress has been made on the knowledge of ionization and recombination rates of iron, an astrophysically abundant heavy element and a major impurity in laboratory fusion devices. We make a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(+25) using the photoionization cross sections of Clark et al. (1986). We provide analytical fits to the recommended data (direct ionization and excitation-autoionization cross sections; radiative and dielectronic recombination rate coefficients). Finally we determine the iron ionic fractions at ionization equilibrium and compare them with previous computations as well as with observational data.

633 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and numerical methods that have affected predictions since the last publicly available version, C84.
Abstract: CLOUDY is a large‐scale spectral synthesis code designed to simulate fully physical conditions within an astronomical plasma and then predict the emitted spectrum. Here we describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and numerical methods that have affected predictions since the last publicly available version, C84. The computational methods and uncertainties are outlined together with the direction future development will take. The code is freely available and is widely used in the analysis and interpretation of emission‐line spectra. Web access to the Fortran source for CLOUDY, its documentation Hazy, and an independent electronic form of the atomic database is also described.

2,571 citations

Journal ArticleDOI
TL;DR: In this paper, a contract for the development and flight of an experiment to study the solar atmosphere with excellent spatial and temporal resolution; and reduction and analysis of the resultant data is presented.
Abstract: This contract is for the development and flight of an experiment to study the solar atmosphere with excellent spatial and temporal resolution; and reduction and analysis of the resultant data. After being launched into a near perfect orbit on 2 April 1998, the spacecraft and instrument remain in good condition and the resultant data are spectacular. Over 6.6 million images have now been taken. Observing highlights this month included several coordinations with CDS, studies of the quiet Sun with SUMER and NMI, coordinations with observers at the SPO Dunn Tower Telescope, and a variety of active region observations. Some of the latter were relatively unique in that they emphasized using the hottest (284A) channel of TRACE. We were informed of the results of the Senior Review Committee's evaluation of all Space Science on-orbit missions and the corresponding fiscal year budgets for TRACE. The budget for FY-02 is modestly less than is being spent in FY-01 and for the years beyond that it is much, much lower.

1,149 citations

Journal ArticleDOI
02 Aug 2001-Nature
TL;DR: In this paper, angle-resolved photoemission spectroscopy was used to study electron velocities and scattering rates in three different families of copper oxide superconductors.
Abstract: Coupling between electrons and phonons (lattice vibrations) drives the formation of the electron pairs responsible for conventional superconductivity. The lack of direct evidence for electron-phonon coupling in the electron dynamics of the high-transition-temperature superconductors has driven an intensive search for an alternative mechanism. A coupling of an electron with a phonon would result in an abrupt change of its velocity and scattering rate near the phonon energy. Here we use angle-resolved photoemission spectroscopy to probe electron dynamics-velocity and scattering rate-for three different families of copper oxide superconductors. We see in all of these materials an abrupt change of electron velocity at 50-80 meV, which we cannot explain by any known process other than to invoke coupling with the phonons associated with the movement of the oxygen atoms. This suggests that electron-phonon coupling strongly influences the electron dynamics in the high-temperature superconductors, and must therefore be included in any microscopic theory of superconductivity.

1,060 citations

Journal ArticleDOI
TL;DR: In this paper, a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...
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...

1,055 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present the results from a comprehensive grid of models computed with their code, which has now been extended to include what they consider to be all energetically important ionization states and transitions.
Abstract: X-ray ionized reflection occurs when a surface is irradiated with X-rays so intense that its ionization state is determined by the ionization parameter ξ ∝ F/n, where F is the incident flux and n the gas density. It occurs in accretion, on to compact objects including black holes in both active galaxies and stellar-mass binaries, and possibly in gamma-ray bursts. Computation of model reflection spectra is often time consuming. Here we present the results from a comprehensive grid of models computed with our code, which has now been extended to include what we consider to be all energetically important ionization states and transitions. This grid is being made available as an ionized-reflection model, REFLION, for XSPEC. Ke yw ords: accretion, accretion discs ‐ line: formation ‐ radiative transfer ‐ galaxies: active ‐ X-rays: general.

831 citations