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Atomic and Molecular Data Preparation and Evaluation for Planetary Applications, 15-9140

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Principal Investigators
Walter F. Huebner
Richard Link

Inclusive Dates: 04/04/99 - 08/12/99

Background - Analysis, modeling, and interpretation of ground- and space-based data for solar system bodies require many types of basic atomic and molecular data, such as: cross-sections and rate coefficients for photon, electron, and heavy-particle collisions, chemical rate coefficient and kinetics data, g-factors for resonance fluorescence, transition coefficients, radiative lifetimes, line strengths, and thermodynamic properties. For investigators working on the analysis of solar system measurements, the effort to collect the relevant data can be time consuming. Also, laboratory or theoretical calculations of atomic and molecular parameters may often be in poor agreement. To address this need within the planetary and space science communities, SwRI developed a prototype web-enabled database of critically evaluated basic atomic and molecular data at http://amop.space.swri.edu.

Approach - The web database builds upon data not previously available in electronic form: the extensive photon cross-section compilation of Huebner et al. [1992]. In this project, the team 1) developed new photon cross-sections and calculated lifetimes, rate coefficients, and excess energies of sodium (Na)-bearing molecules known to exist in comets, 2) compiled photon and electron impact cross-sections for CO2 and O/N2 atmospheres, for use in calculating photoelectron fluxes in the atmospheres of Venus and Neptune's moon Triton, and 3) established the fundamentals for determining g-factors, resonance fluorescence calculations, and acceleration of atoms and molecules by radiation pressure.

Accomplishments - An interactive, web-enabled database has been developed to address the need for readily available atomic and molecular data required for the analysis and interpretation of space mission data. The web server plots and provides downloads of 1) critically evaluated cross-section data, as well as rate coefficients and excess energies for 2) blackbody, 3) interstellar, and 4) solar radiation fields for user-selected atoms and molecules. Currently, the database contains photon data for nearly 100 atoms and molecules and is continually being upgraded and expanded.

Photoelectron calculations were performed for the upper atmospheres of Venus, Mars, and Triton, and the sodium results have been applied to the study of the molecular chemistry of comets. The results of these two endeavors have been presented at several scientific meetings, and so far one paper has been submitted for publication. The numerical results will be made publicly available in the database (after publication). The Mars photoelectron results are described at the  Mars Express/Aspera-3 website.

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