John J. Keady

Solar photo rates for planetary atmospheres and atmospheric pollutants

Unattenuated solar photo rate coefficients and excess energies for dissociation, ionization, and dissociative ionization are presented for atomic and molecular species that have been identified or are suspected to exist in the atmospheres of planets, satellites (moons), comets, or as pollutants in the Earth atmosphere. The branching ratios and cross sections with resonances have been tabulated to the greatest detail possible and the rate coefficients and excess energies have been calculated from them on a grid of small wavelength bins for the quiet and the active Sun at 1 AU heliocentric distance.

Detection of C3 in the Circumstellar Shell of IRC+10216

The C5 molecule has been identified in the infrared spectrum of the prototypical obscured carbon star, IRC+10216. In addition to their astrophysical importance, pure carbon chain molecules such as C5 are of interest in the chemistry of flames and propellants.

Helioseismic Tests of the New Los Alamos LEDCOP Opacities

We compare the helioseismic properties of two solar models, one calibrated with the OPAL opacities and the other with the recent Los Alamos LEDCOP (Light Element Detailed Configuration Opacity) opacities. We show that, in the radiative interior of the Sun, the small differences between the two sets of opacities (up to 6% near the base of the convection zone) lead to noticeable differences in the solar structure (up to 0.3% in sound speed), with the OPAL model being the closest to the helioseismic data. More than half of the difference between the two opacity sets results from the interpolation scheme and from the relatively widely spaced temperature grids used in the tables. The remaining 3% intrinsic difference between the OPAL and the LEDCOP opacities in the radiative interior of the Sun is well within the error bars on the opacity calculations resulting from the uncertainties on the physics. We conclude that both the OPAL and LEDCOP opacities produce solar models in close agreement with helioseismic inferences, but discrepancies still persist at the level of 0.6% between the calculated and inferred sound speed in the radiative interior of the Sun.

C2H in the 2 micron infrared spectrum of IRC +10216

Nearly 30 lines of C/sub 2/H in two bands at 4011 and 4108/cm have been identified in the 2 micron spectrum of IRC +10216. A rotational temperature of about 12.5 + or - 1.5 K and a column density of about 3 X 10 to the 15/sq cm have been found. Modeling the lines with an observers frame radiative transfer code indicates that the peak radial abundance of C/sub 2/H relative to H/sub 2/ is about 0.00001-0.000001, and that the C/sub 2/H is concentrated about 8 X 10 to the 16 cm away from the central infrared source. A model including photodissociation by interstellar UV demonstrates that all the observed C/sub 2/H can be formed in the circumstellar shell by photolysis of C/sub 2/H/sub 2/. It is suggested that the radial abundance of C/sub 2/H/sub 2/ decreases by at least a factor of 5, perhaps by accretion of C/sub 2/H/sub 2/ onto grains, from about 100 solar radii to about 1000 solar radii, where photodissociation begins. 39 references.

Quantum Molecular Dynamics calculations of radiative opacities

We show that Quantum Molecular Dynamics provides a powerful tool to extend and benchmark current opacities libraries into the complex regime of warm dense matter. In this regime, the medium can be constituted of electrons, protons, atoms and molecules, while plasma and many-body effects can not be treated as perturbations. Among the most notable features of this new approach for calculating Rosseland mean opacities is the ability to obtain a consistent set of material (equation-of- state), optical and electrical properties for various mixtures from the same simulation.

PROGRESS IN LTE AND NON-LTE RADIATIVE TRANSPORT PROPERTIES

Atomic processes in ionized gases are reviewed along with recent calculations. Opacity calculations in progress at Los Alamos are described. Several of the open issues in the calculations relevant to opacities are discussed and preliminary results of the new advances are illustrated.

Atomic configuration average simulations for plasma spectroscopy

Configuration average atomic physics based on Hartree-Fock methods and an unresolved transition array (UTA) simulation theory are combined to provide a computationally efficient approach for calculating the spectral properties of plasmas involving complex ions. The UTA theory gives an overall representation for the many lines associated with a radiative transition from one configuration to another without calculating the fine structure in full detail. All of the atomic quantities required for synthesis of the spectrum are calculated in the same approximation and used to generate the parameters required for representation of each UTA, the populations of the various atomic states, and the oscillator strengths. The authors use this method to simulate the transmission of X-rays through an aluminium plasma. The results are compared to experiment and to previous detailed fine structure calculations. The present results duplicate all major structural features of the spectrum and represent a significant saving in computational time compared to detailed calculations.

Early Solar Mass Loss, Opacity Uncertainties, and the Solar Abundance Problem

Solar models calibrated with the new element abundance mixture of Asplund et al. published in 2005 no longer produce good agreement with the sound speed, convection zone depth, and convection zone helium abundance inferred from solar oscillation data. Attempts to modify the input physics of the standard model, for example, by including enhanced diffusion, increased opacities, accretion, convective overshoot, or gravity waves have not restored the good agreement attained with the prior abundances. Here we present new models including early mass loss via a stronger solar wind. Early mass loss has been investigated prior to the solar abundance problem to deplete lithium and resolve the ‘faint early sun problem’. We find that mass loss modifies the core structure and deepens the convection zone, and so improves agreement with oscillation data using the new abundances; however the amount of mass loss must be small to avoid destroying all of the surface lithium, and agreement is not fully restored. We also cons...

Temporal Variations of CO Infrared Lines in Cool-Star Winds

High-resolution infrared spectroscopy of molecular lines provides a powerful diagnostic probe to investigate the spatial structure and temporal evolution of the cool, dusty winds of Miras and long—period variables, such as the carbon rich IR-Mira IRC+10216 (Keady et al. 1988). For this object, high-resolution spectra of the CO fundamental and first overtone transitions at 5μm and 2μm have been obtained repeatedly over an interval spanning more than ten years. The unsaturated overtone lines reflect the actual conditions and their temporal changes in the acceleration region of the wind. The line profiles show a multi-component absorption structure, and spectra from different epochs reveal changes of the line profiles (e.g., the emergence of a new absorption component) on time scales that are much longer than the period of the star (Sada 1993).

Quantum Molecular Dynamics Calculations of Rosseland Mean Opacities

We show that Quantum Molecular Dynamics provides a powerful tool to extend and benchmark current opacity libraries into the complex regime of warm dense matter. In this regime, the medium can be constituted of electrons, protons, atoms and molecules, while plasma and many body effects can not be treated as perturbations. Among the most notable features of this new approach for calculating Rosseland mean opacities is the ability to obtain a consistent set of material, optical and electrical properties for various mixtures from the same simulation.