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.

https://iopscience.iop.org/article/10.1086/316190/pdf

CLOUDY 90: Numerical Simulation of Plasmas and Their Spectra

We report the first demonstration of a technique by which an optically thick medium may be rendered transparent. The transparency results from a destructive interference of two dressed states which are created by applying a temporally smooth coupling laser between a bound state of an atom and the upper state of the transition which is to be made transparent. The transmittance of an autoionizing (ultraviolet) transition in Sr is changed from exp(-20) without a coupling laser present to exp(-1) in the presence of a coupling laser.

https://link.aps.org/pdf/10.1103/PhysRevLett.66.2593

Observation of electromagnetically induced transparency.

CHIANTI consists of a critically evaluated set of atomic data and transition probabilities necessary to calculate the emission line spectrum of astrophysical plasmas. The data consist of atomic energy levels, atomic radiative data such as wavelengths, weighted oscillator strengths and A values, and electron collisional excitation rates. A set of programs that use these data to calculate the spectrum in a desired wavelength range as a function of temperature and density is also provided. A suite of programs has been developed to carry out plasma diagnostics of astrophysical plasmas. The state-of-the-art contents of the CHIANTI database will be described and some of the most important results obtained from the use of the CHIANTI database will be reviewed.

/pdf/chianti-an-atomic-database-for-emission-lines-i-wavelengths-1btihffpr5.pdf

CHIANTI - an atomic database for emission lines - I. Wavelengths greater than 50 Å

a b s t r a c t The ab initio quasirelativistic Hartree–Fock method developed specifically for the calculation of spectral parameters of heavy atoms and highly charged ions is used to derive transition data for a multicharged tungsten ion. The configuration interaction method is applied to include electron correlation effects. The relativistic effects are taken into account in the Breit–Pauli approximation for quasirelativistic Hartree–Fock radial orbitals. The energy level spectra, radiative lifetimes and Lande gfactors are calculated for the 4p 6 4d 2 , 4p 6 4d4f, and 4p 5 4d 3 configurations of the ion W 36+ . The transition wavelengths, spontaneous transition probabilities, oscillator strengths, and line strengths for the electric dipole, electric quadrupole, electric octupole, and magnetic dipole transitions among the levels of these configurations are tabulated.

Atomic Data and Nuclear Data Tables

The isolation of graphene has triggered an avalanche of studies into the spin-dependent physical properties of this material, as well as graphene-based spintronic devices Here we review the experimental and theoretical state-of-art concerning spin injection and transport, defect-induced magnetic moments, spin-orbit coupling and spin relaxation in graphene Future research in graphene spintronics will need to address the development of applications such as spin transistors and spin logic devices, as well as exotic physical properties including topological states and proximity-induced phenomena in graphene and other 2D materials

Graphene Spintronics

Atomic Transition Probabilities

NIST Atomic Spectra Database (version 2.0)

Atomic Spectra Database

The Stark-broadened profiles of the Balmer lines ${\mathrm{H}}_{\ensuremath{\alpha}}$, ${\mathrm{H}}_{\ensuremath{\beta}}$, ${\mathrm{H}}_{\ensuremath{\gamma}}$, and ${\mathrm{H}}_{\ensuremath{\delta}}$, have been measured in a high-current, wall-stabilized arc operated in hydrogen. Temperatures and electron densities have been determined with a plasma model assuming partial local thermodynamic equilibrium (LTE), after a detailed plasma analysis revealed small deviations from complete LTE. The temperatures have been determined from line-to-continuum intensity ratios using ${\mathrm{H}}_{\ensuremath{\beta}}$ and continuum points in the near uv, and the electron densities were derived from absolute intensity measurements. The investigations cover the range of electron densities between 1.5 \ifmmode\times\else\texttimes\fi{} ${10}^{16}$ and ${10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ and temperatures between 0.9 \ifmmode\times\else\texttimes\fi{} ${10}^{4}$ and 1.4 \ifmmode\times\else\texttimes\fi{} ${10}^{4}$ K. Extensive comparisons with recent Stark-broadening theories and other experiments have been undertaken with the following principal results: The most pronounced differences between this experiment and theory occur in and near the line centers, where the measured profiles show systematically less structure than the calculations predict. Comparisons of the calculated and precisely measured ratios between the \textonehalf{}, \textonequarter{}, and $\frac{1}{8}$ widths within each line show that the recent theories are internally consistent within 6% for ${\mathrm{H}}_{\ensuremath{\beta}}$ and ${\mathrm{H}}_{\ensuremath{\gamma}}$, whereas for ${\mathrm{H}}_{\ensuremath{\alpha}}$ inconsistencies of order 25% occur. Similar inconsistencies, somewhat larger respectively, are found for the theoretical values of the half-width ratios between different Balmer lines. For the most important line ${\mathrm{H}}_{\ensuremath{\beta}}$, the measured half-widths agree within 7% with the calculated values. The total experimental error in this comparison, which originates predominantly in the electron-density measurement, is estimated not to exceed 6%. Very reproducible asymmetries and red shifts are observed for ${\mathrm{H}}_{\ensuremath{\beta}}$ and ${\mathrm{H}}_{\ensuremath{\gamma}}$. Somewhat smaller red shifts are also obtained for ${\mathrm{H}}_{\ensuremath{\alpha}}$. The shifts are approximately linear functions of the electron density. Comparisons with other experimental data show appreciable scatter between the various results. We estimate that for the most-often-studied line ${\mathrm{H}}_{\ensuremath{\beta}}$ the uncertainties in the theoretical Stark widths are of the order of (5-7)% for the range of our experiment.

Detailed Study of the Stark Broadening of Balmer Lines in a High-Density Plasma

A summary of the contents and features of the new NIST Atomic Spectra Database is presented. All material in this large database has been obtained from critical data assessments done over the last 30 years. Only reference data, i.e., data fulfilling certain quality requirements, are included. For each spectral line and energy level, one numerical value—the “best” available value—is tabulated.

Daniel E. Kelleher

Papers

Atomic Transition Probabilities

NIST Atomic Spectra Database (version 2.0)

Atomic Spectra Database

Detailed Study of the Stark Broadening of Balmer Lines in a High-Density Plasma

NIST Atomic Spectra Database