Daniel Savin
(Columbia University and Visitor of Weizmann Institute)

Uncertainties in Chemical Abundances and the Metagalactic Radiation Field 
at High Redshift

Many fundamental questions of cosmology can be addressed through
spectroscopic observations of high redshift clouds in the intergalactic
medium. For example, observations of C II, C IV, and Si IV absorption
lines can be used to constrain the chemical evolution of the universe as
well as the spectral shape and history of the metagalactic radiation
field. However, our ability to infer the properties of these high
redshift objects is limited by uncertainties in the atomic data used to
interpret the spectroscopic observations. I will discuss some of the
astrophysical implications of the uncertainties in the atomic data base
and present recent laboratory measurements designed to improve the needed
atomic data.