9612366 Slanger Excited states of molecular oxygen are ubiquitous throughout the atmosphere, and their spectroscopy, radiative properties, and kinetics are essential elements in determining the photophysics and photochemistry of atmospheric regions. In this project, three areas will be investigated: a) kinetics and reactivity of the O2(b) state in vibrationally excited levels, b) weakly bound but potentially important states of O2 lying near the dissociation limit, and c) exploration of isotope effects in O2 photoabsorption in the 242-250 nm Herzberg band absorption region. The O2(b) state has been studied primarily in its lowest vibrational level, yet there are indications of stratospheric sources involving much higher vibrational levels, and their kinetic properties could be important. The weakly-bound states of O2 have been discussed in various contexts, yet there are no relevant measurements. The technique of cavity ring-down spectroscopy is making it possible to investigate these states, which are implicated as precursors in both laboratory and atmospheric phenomena. Variability in atmospheric oxygen isotope ratios in ozone, carbon dioxide, and nitrous oxide are of current interest, and cavity ring-down studies may be helpful in explaining these effects. ***
