Electron transmission studies in a free jet: molecular oxygen

A new apparatus incorporating an electron transmission spectrometer and a free jet has been used to study temporary negative-ion formation in O2. The resonant vibrational levels of the ground electronic state of O2- ( nu "=4-12) were observed as spin-orbit doublets, consistent with previous experimental results. The vibrational constants of O2-, an upper bound on the autodetachment width of the nu "=4 vibrational level and the relative electron attachment cross sections into the vibrational levels ( nu "=5-12) have been determined. A velocity broadening term, stemming from the use of an uncollimated free jet, has also been calculated. Measurements of resonances in Ar and He were used to verify the magnitude of this term and permitted the instrument function to be extracted as well.