Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session M8: Invited Session: Applications of Spectroscopy in AstrophysicsInvited
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Sponsoring Units: GPC Chair: Brad Marston, Brown University Room: 555AB |
Thursday, May 26, 2016 8:00AM - 8:30AM |
M8.00001: Tropospheric Emissions: Monitoring of Pollution (TEMPO) -- Status and Potential Science Studies Invited Speaker: Kelly Chance TEMPO is the first NASA Earth Venture Instrument, to launch between 2019 and 2021. It measures atmospheric pollution from Mexico City and Cuba to the Canadian oil sands, and from the Atlantic to the Pacific, hourly at high spatial resolution, \textasciitilde 10 km$^{\mathrm{2}}$. It measures the key elements of air pollution chemistry. Geostationary (GEO) measurements capture the variability in the diurnal cycle of emissions and chemistry at sub-urban scale to improve emission inventories, monitor population exposure, and enable emission-control strategies. TEMPO measures the UV/visible spectra to retrieve O$_{\mathrm{3}}$, NO$_{\mathrm{2}}$, SO$_{\mathrm{2}}$, H$_{\mathrm{2}}$CO, C$_{\mathrm{2}}$H$_{\mathrm{2}}$O$_{\mathrm{2}}$, H$_{\mathrm{2}}$O, aerosols, cloud parameters, and UVB radiation. It tracks aerosol loading. It provides near-real-time air quality products. TEMPO is the North American component of the global geostationary constellation for pollution monitoring, with the European Sentinel-4 and the Korean GEMS. TEMPO studies may include: Solar-induced fluorescence from chlorophyll over land and in the ocean to study tropical dynamics, primary productivity, carbon uptake, to detect red tides, and to study phytoplankton; Measurements of stratospheric intrusions that cause air quality exceedances; Measurements at peaks in vehicle travel to capture the variability in emissions from mobile sources; Measurements of thunderstorm activity, including outflow regions to better quantify lightning NO$_{\mathrm{x}}$ and O$_{\mathrm{3}}$ production; Cropland measurements follow the temporal evolution of emissions after fertilizer application and from rain-induced emissions from semi-arid soils; Measurements investigate the chemical processing of primary fire emissions and the secondary formation of VOCs and ozone; Measurements examine ocean halogen emissions and their impact on the oxidizing capacity of coastal environments; Spectra of nighttime lights are markers for human activity, energy conservation, and compliance with outdoor lighting standards intended to reduce light pollution. [Preview Abstract] |
Thursday, May 26, 2016 8:30AM - 9:00AM |
M8.00002: Modeling of low-temperature plasmas generated using laser-induced breakdown spectroscopy: the ChemCam diagnostic tool on the Mars Science Laboratory Rover Invited Speaker: James Colgan We report on efforts to model the low-temperature plasmas generated using laser-induced breakdown spectroscopy (LIBS). LIBS is a minimally invasive technique that can quickly and efficiently determine the elemental composition of a target and is employed in an extremely wide range of applications due to its ease of use and fast turnaround. In particular, LIBS is the diagnostic tool used by the ChemCam instrument on the Mars Science Laboratory rover {\it Curiosity}. In this talk, we report on the use of the Los Alamos plasma modeling code ATOMIC to simulate LIBS plasmas, which are typically at temperatures of order 1~eV and electron densities of order $10^{16-17}$ cm$^{-3}$. At such conditions, these plasmas are usually in local-thermodynamic equilibrium (LTE) and normally contain neutral and singly ionized species only, which then requires that modeling must use accurate atomic structure data for the element under investigation. Since LIBS devices are often employed in a very wide range of applications, it is therefore desirable to have accurate data for most of the elements in the periodic table, ideally including actinides. Here, we discuss some recent applications of our modeling using ATOMIC that have explored the plasma physics aspects of LIBS generated plasmas, and in particular discuss the modeling of a plasma formed from a basalt sample used as a ChemCam standard$^1$. We also highlight some of the more general atomic physics challenges that are encountered when attempting to model low-temperature plasmas. The Los Alamos National Laboratory is operated by Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under Contract No. DE-AC5206NA25396. $^1$ J. Colgan, E. J. Judge, H. M. Johns, D. P. Kilcrease, J. E. Barefield II, R. McInroy, P. Hakel, R. C. Wiens, and S. M. Clegg, Spectrochimica Acta B {\bf 110}, 20--30 (2015). [Preview Abstract] |
Thursday, May 26, 2016 9:00AM - 9:30AM |
M8.00003: Spectroscopically Unlocking Exoplanet Characteristics Invited Speaker: Nikole Lewis Spectroscopy plays a critical role in a number of areas of exoplanet research. The first exoplanets were detected by precisely measuring Doppler shifts in high resolution (R$\sim$100,000) stellar spectra, a technique that has become known as the Radial Velocity (RV) method. The RV method provides critical constraints on exoplanet masses, but is currently limited to some degree by robust line shape predictions. Beyond the RV method, spectroscopy plays a critical role in the characterization of exoplanets beyond their mass and radius. The Hubble Space Telescope has spectroscopically observed the atmospheres of exoplanets that transit their host stars as seen from Earth giving us key insights into atmospheric abundances of key atomic and molecular species as well as cloud optical properties. Similar spectroscopic characterization of exoplanet atmospheres will be carried out at higher resolution (R$\sim$100-3000) and with broader wavelength coverage with the James Webb Space Telescope. Future missions such as WFIRST that seek to the pave the way toward the detection and characterization of potentially habitable planets will have the capability of directly measuring the spectra of exoplanet atmospheres and potentially surfaces. Our ability to plan for and interpret spectra from exoplanets relies heavily on the fidelity of the spectroscopic databases available and would greatly benefit from further laboratory and theoretical work aimed at optical properties of atomic, molecular, and cloud/haze species in the pressure and temperature regimes relevant to exoplanet atmospheres. [Preview Abstract] |
Thursday, May 26, 2016 9:30AM - 10:00AM |
M8.00004: Astrophysics with Laboratory X-ray and EUV spectroscopy Invited Speaker: Peter Beiersdorfer Improvements in the spectral resolution of x-ray observatories have necessitated increasing accuracies in the spectral models used in the analysis of astrophysical data. In response, we have been carrying out laboratory measurements to assess the fidelity of the atomic data used in the models and to calibrate specific spectral diagnostics. The goal is to meet the current need for spectroscopic models to be able to predict line intensities on the order of a few percent for the strongest transitions and to represent line positions with spectroscopic accuracy. Our spectroscopy measurements are performed in the extreme ultraviolet and x-ray regimes and are mostly carried out at the electron beam ion trap facility at Livermore, which produces the relevant ions in a density and temperature environment similar to those of astrophysical plasmas. Examples discussed in this talk fall into four categories. (1) The identification of lines seen in astrophysical spectra but missing in the models; (2) the establishment of benchmark wavelengths for K-shell transitions in M-shell ions and for L-shell transitions in L-shell ions needed for the interpretation of absorption line features; (3) the calibration of the line emission of key spectroscopic diagnostics, such as the L-shell lines of Fe XVII; (4) the disentanglement of line excitation processes, especially those associated with charge exchange, that produce x-ray emission from comets, planets, and the interstellar medium. [Preview Abstract] |
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