This research is a continuation of an ongoing laboratory study of thermal energy charge transfer among atoms and ions of astrophysical interest. It has long been known that thermal energy charge transfer plays an important role in determining the ionization structure, thermal structure, emission spectrum and absorption spectrum for a range of cosmic plasmas. These include photoionized gas found in planetary nebulae, H II regions, Wolf-Rayet nebulae, luminous blue variable nebulae, Lyman alpha clouds, and the intergalactic medium; shocks in supernova remnants and Herbig-Haro objects; and primordial gas clouds during the epoch of protogalaxy and first star formation. Unfortunately, many theoretical calculations carried out during the past 25 years in response to the demand for reliable thermal energy charge transfer data are reliable to only a factor of 3-10. And while the latest state-of-the-art calculations are expected to be more reliable, such efforts are less common and can still be off by a factor of 3 when not benchmarked against experiments. However, few laboratory measurements exist despite the demand from the community. To address this need, an ongoing series of laboratory measurements of thermal energy charge transfer will be continued using the Oak Ridge National Laboratory ion-atom merged-beams apparatus. Here, measurements will be made of the thermal energy charge transfer of C2+, O+, O2+, Se3+, and Kr2+. Reliable charge transfer data for the cosmically abundant C2+, O+, and O2+ are needed for modeling planetary nebulae and H II regions as well as shocks in supernovae remnants and Herbig-Harrow objects. Data for Se3+ and Kr2+ are needed to analyze planetary nebula spectra in order to study both nucleosynthesis via the slow neutron capture process and convective dredge-up in the planetary nebula progenitor stars. These results will be used to produce rate coefficients with an estimated accuracy of * 20% and will provide fits for plasma modeling. Modern charge transfer theory will also be benchmarked against these results. Finally, the laboratory apparatus will be modified so that the metastable fraction in the ion beams can be measured and controlled. For beams with a significant metastable fraction, this will allow the extraction of absolute cross sections for both the ground state and metastable ions in the beam. This new capability will further increase the uniqueness of the Oak Ridge National Laboratory ion-atom merged-beams apparatus. The training and professional preparation of a graduate student will be supported. This student will carry out a large portion of the project in partial fulfillment of the requirements for the degree of Doctor of Philosophy. The results of this research will be presented via seminars and colloquia to colleagues in academia, government, and industry. Reports at national and international conferences will be given and published in the appropriate journals. In addition, this work will further enhance the Columbia/Oak Ridge National Laboratory infrastructure for research and education. Prof. Gary Ferland at the University of Kentucky will input the new rate coefficients into CLOUDY which is one of the most commonly used codes for modeling photoionized gas.
