Shape-resonance-induced non-Franck–Condon effects in the valence-shell photoionization of O2

Non-Franck–Condon effects in the valence-shell photoionization spectrum of O2 are studied using the multiple scattering model. Calculations for the 3σg, 1πu, and 1πg levels indicate that the enhanced sensitivity of dipole strengths to internuclear separation, induced by shape resonances, reduces and broadens the resonant cross section; nonresonant channels are negligibly affected. The resulting cross sections and asymmetry parameters show fair overall agreement with line and continuum source measurements.