EXPERIMENTAL DIFFERENTIAL CROSS-SECTIONS FOR THE ELECTRON-IMPACT EXCITATION OF THE A 1-DELTA(G),B(1)SIGMA(-2()(G), AND THE 6 EV STATES OF O)

Absolute differential cross sections for the excitation of the a (1) D elta(g) and b (1) Sigma(g)(+) states in O-2 were measured at 90 degree s, and in some cases at 30 degrees as a function of electron energy fr om threshold up to about 18 eV and, at 4.5 and 75 eV, as a function of scattering angle from 10 degrees to 135 degrees. The cross sections w ere obtained for the upsilon = 0, and the energy dependence also for s elected higher vibrational states up to upsilon = 19. The cross sectio ns agree, within the error bars, with earlier data as far as absolute magnitude and general appearance of the curves are concerned, but ther e are differences in finer details of the shape of the curves. The ups ilon = 0 cross sections exhibit two broad resonance bands at about 4 e V and about 8 eV for both the a (1) Delta(g) and b (1) Sigma(g)(+) sta tes. The cross sections compare favourably with the recent calculation s of Noble, Burke and co-workers, except for a larger width of the 8 e V resonance in the experiment. A comparison with theory permits a tent ative assignment of the 4 eV and 8 eV bands as X (2) Pi(g) and A (2) P i(u) resonances. The cross sections for exciting upsilon = 2 and highe r levels of the a and b states consist of one band at 6.5 eV, identica l in shape to the dissociative attachment (DA) band. The energy depend ence of the excitation of the (...pi(U)(3) pi(g)(3)) 6 eV band at 90 d egrees has also been measured and is compared to the earlier experimen t and theory of Teillet-Billy et al.