The speaker will be Dr. Daniel Wolf Savin
Place: Holcblat Hall
Time: Wednesday, 21/May/2003, 14:00
Title: Atomic Physics at High Redshift and Near Black Holes
Atomic physics plays an important role in determining the spectrum and thermal structure of cosmic photoionized plasmas formed in the early universe (i.e., at high redshift) and near black holes. Spectra from these sources can be used to address issues such as the primordial helium abundance, the chemical evolution of the universe, the shape of the metagalactic radiation field as a function of redshift, and the structure of accretion disks in the vicinity of neutron stars and black holes. However, our ability to infer the astrophysical properties of these sources can be limited by our understanding of atomic physics. Of particular importance are accurate low temperature dielectronic recombination (DR) rate coefficients. Low temperature DR is the dominant electron-ion recombination process for most ions in photoionized plasmas. Existing uncertainties in the theoretical DR rate coeffficients limit our ability to address the above mentioned issues. I will discuss some of the astrophysical implications of the uncertainties in the DR rate coefficients currently used for modeling cosmic plasmas. I will also present recent experimental work we have carried out to help resolve these issues.