Knowledge Bank

Electron impact on $O2$ can dissociate it into atoms with several eV of translational kinetic energy. From measurements of this kinetic energy (by the time-of-flight method) and from knowledge of the electronic states of the fragment atoms, repulsive potential curves can be determined. In this experiment, the detector is sensitive only to metastable states; in the oxygen atom these states are 3s at 9.1 eV and long-lived high-lying Rydberg states ($n\sim$25). These high Rydberg atoms are formed by dissociation of high Rydberg molecules, which have potential curves that follow very closely those for the limiting ionic states. Consequently, these studies of neutral metastable states provide spectroscopic information on the $O2-$ ion as well as the neutral $O2$ molecule.