Spin endash orbit branching ratios for photoionization of the 3dπ gerade states of O2: Evidence for preferential ionization of the Ωc=3/2 core states

We have obtained high-resolution photoelectron spectra for eight of the ten 3dπ electronic states of O2, using a rotationally resolved, two-color 2+1' excitation and ionization scheme. A magnetic bottle photoelectron spectrometer, used to acquire the spectra, provided a resolution sufficient to observe the yields of the individual spin endash orbit states of the ground electronic state of the ion. Branching ratios were obtained from the spectra for three different photoionization wavelengths. The overall behavior of the branching ratios for different electronic states can be explained by calculating the core state composition of the intermediate states, taking into account the spin endash orbit mixing of Hund close-quote s case (a) basis states, and assuming that electronic states having the core state Ωc=3/2 have a larger photoionization probability than those having an Ωc=1/2 core. copyright 1996 American Institute of Physics