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The double-charge-transfer (DCT) spectrum of O 2 2+ has been recorded at 140 meV resolution using 1.5 keV H + projectiles. Electronic bands of the low-lying triplet states, namely A 3 ⌺ u + , W 3 ⌬ u , B 3 ⌸ g , and BЈ 3 ⌺ u − , have been resolved. Assuming that the observed bands directly reflect the Franck-Condon (FC) profiles, potentialenergy curves of the A 3 ⌺ u + , W 3 ⌬ u , and BЈ 3 ⌺ u − states within the FC region are determined based on the reflection approximation. For a quantitative check of the results, complete active space self-consistent-field and multireference configuration-interaction calculations have been performed to predict the potential-energy curves and the FC profiles. The calculated energy curves agree well with the experimentally derived ones. The theoretical FC profiles reproduced well the band shapes observed by both present DCT and previous Dopplerfree kinetic-energy release methods. However, our results cast doubt on the previous assignment of luminescence to the O 2 2+ B 3 ⌸ g → A 3 ⌺ u + transition and the observed bound level of the A 3 ⌺ u + state by the previous threshold photoelectron coincidence experiment.

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Polarization of the (n + 1) 3 S → n 3 P J radiation from Zn and Cd atoms (n = 4 for Zn and 5 for Cd, respectively) was observed after electron impact with energy slightly above the n 1 S → (n + 1) 3 S threshold excitation energy. The observing direction was perpendicular to both the incident electron beam and the atomic beam. All of the triplet radiation (J = 0, 1 and 2) was slightly polarized. The observed fractional polarization degrees were −5.4, 3.8 and −0.8% corresponding to J = 0, 1 and 2 spectra in the final 3 P J states of the Zn atom and −6.9, 4.3 and −1.0% for the Cd atom. These values could be explained by assuming populations in the sublevels M S = 0 and ±1 of the (n + 1) 3 S states deviating from an equal mean value of 1 3 for each sublevel. It is interesting and reasonable that the deviations determined independently for different states coincided with each other quite well. The deviated values of fractional population for the sublevel M S = 0 were 0.36 for Zn and 0.37 for Cd, respectively.