OBSERVATION OF AUTOIONIZATION IN O2 BY AN ELECTRON-ELECTRON COINCIDENCE METHOD

A strong transition to an autoionizing state has been observed in O2 a t 16.83 +/- 0.11 eV by means of a new electron-electron coincidence me thod. The method uses the fact that electrons arising from autoionizin g states appear at a constant energy loss corresponding to the excitat ion energy of the autoionizing state rather than at a constant ionizat ion potential as do electrons produced by direct ionization. Compariso n of the present data with previous photoionization studies suggests t hat the autoionizing O2 state is the same state deduced to be responsi ble for abnormal vibrational intensities in the O2+X2PI(g) ground stat e when 16.85 eV Ne(I) photons are used. These electron-electron coinci dence experiments provide a direct new method for the study of autoion ization produced by electron impact.