Speaker: Mark Thiemens, UCSD [speaker's website]
The observation of mass independent isotopic molecular species in atmospheres, present and past; terrestrial and extra terrestrial have lead to new understandings that would not have been otherwise recognized. This field originated and continues from a combination of recognizing and theoretically developing new quantum mechanically based isotope effects and, from measurements in a variety of environments.

A significant facet has been understanding the oxidative capacity of the earth, present and past. The work has applications to the carbon cycle as well as upper atmospheric ozone. Its variation through time has tracked the ozone and oxygen cycle on billion year time scale; both on Earth and Mars. New advances in the basic physical chemistry of photolysis has deepened understanding of the origin and evolution of the solar system and, leads to better interpretation of present day atmospheric chemistry.