PHOTOEXCITED K-AUGER SPECTRA OF ATOMIC AND MOLECULAR-OXYGEN

K Auger spectra of the oxygen atom following either 1s photoionization or 1s --> np photoexcitation are presented and compared with energy a nd transition rate calculations where available. Data are juxtaposed t o earlier results on neon, showing that the excellent agreement betwee n theory and experiment which exists for the closed-shell atom neon do es not, at present, extend to the open-shell atom oxygen. Auger spectr a following 1s --> 2p excitation in the O atom and 1s, 2p double ioniz ation in Ne are found to have similar branching ratios. All major line s in the Auger spectra of oxygen could be resolved and fully analyzed with regard to energies, branching ratios, and angular distributions. A strong anisotropy is measured for the Auger transitions associated w ith the 1s --> 2p excitation. The 1sigma(u) --> 1pi(g) and 1sigma(g) - -> 3sigma(u) resonance Auger spectra of molecular oxygen are also pres ented. The angular distributions of the high kinetic energy lines in t he molecular spectra are measured, and the atomic-like Auger lines in the 3sigma(u) decay are compared with the pure atomic 2p decay spectru m. Energies of the Kalpha X-ray transitions in the atom are deduced. T he experimental setup, which allowed us to record these low-Z atomic A uger spectra for the first time, is described in some detail.