Direct measurement of the deactivation rate of excited singlet sigma and singlet delta molecular oxygen by oxygen

Summary form only given. The collisional deactivation of the lowest singlet states of molecular oxygen O/sub 2/(b/sup 1//spl Sigma/) and O/sub 2/(a/sup 1//spl Delta/) is of great interest for many applications (e.g. as energy donors in gas phase transfer kinetics). An interesting feature of these collisions that has been postulated/sup 4/ is that the O/sub 2/(b/sup 1//spl Sigma/) state is quenched exclusively to the (a/sup 1//spl Delta/) state and not to the ground state (X/sup 3//spl Sigma/). Direct measurement of the fraction of O/sub 2/(b/sup 1//spl Sigma/) species quenched to the (a/sup 1//spl Delta/) state is not very easy task because of very long life time of the (a/sup 1//spl Delta/) state (more than 60 minutes) and a long wavelength of the fluorescence emission (1268 nm) from this state to the ground state. In this work we present the first direct measurement of the O/sub 2/(a/sup 1//spl Delta/) deactivation rate, direct measurement of the O/sub 2/(b/sup 1//spl Sigma/) deactivation rate and measurement of the fraction of O/sub 2/(b/sup 1//spl Sigma/) species quenched to the (a/sup 1//spl Delta/) state.