Admin Login • Instructor Login • Student Login

Your Support

Dissertation Defense

Highly-Charged Ion Collisions with Atoms: Applications to X-ray Emission in the Universe  
Guest Speaker
Renata Cumbee  
Guest Affiliation
UGA Physics and Astronomy  
Guest Affiliation Url  
Prof. Phillip Stancil  
Wednesday, July 13, 2016 2:00 pm - 3:00 pm  
Room 322, Physics Building  

Atomic collisions play a fundamental role in astrophysics, plasma physics, and fusion physics. In this dissertation, we focus on charge exchange (CX) between hot ions and neutral atoms relevant to a selection of astronomical environments. Even though charge exchange calculations can provide vital information including neutral and ion density distributions, ion temperatures, elemental abundances, and ion charge state distributions in the environments considered, both theoretical calculations and laboratory studies of these processes lack the necessary reliability and/or coverage. In order to better understand the spectra we observe in astrophysical environments in which both hot plasma and neutral gas are present, includ- ing comets, the heliosphere, supernova remnants, galaxy clusters, star forming galaxies, the outflows of starburst galaxies, and cooling flows of hot gas in the intracluster medium, a thorough CX X-ray model is needed. Included in this model should be a complete set of X-ray line ratios for relevant ion and neutral interactions for a range of energies.

In this work, theoretical charge exchange emission spectra are produced using cross sec- tions calculated with widely applied approaches including the quantum mechanical molecular orbital close coupling (QMOCC), atomic orbital close coupling (AOCC), classical trajectory Monte Carlo (CTMC), and the multichannel Landau-Zener (MCLZ) methods. When possible, theoretical data are benchmarked to experiments. Using a comprehensible, but still far from complete, CX database, new models are performed for a variety of X-ray emitting environments. In an attempt to describe the excess emission in X-rays of the starburst galaxy M82, Ne X CX line ratios are compared to line ratios observed in the region. A more com- plete XSPEC X-ray emission model is produced for H-like and He-like C-Al ions colliding with H and He for a range of energies; 200, 300, 500, 700, 1000, 2000, 3000, and 5000 eV/u. This model is applied to the northeast rim of the Cygnus Loop supernova remnant in an attempt to determine the contribution of CX to that region. The database is also applied to a preliminary model of the fast and slow solar wind interacting with the heliosphere.

Index words: atomic processes, galaxies: individual: M82, galaxies: starbursts, ISM: supernova remnants, line: formation, X-rays: general, X-rays: ISM, X-rays: galaxies