Momentum transfer dependence behaviors of ionization and dissociation of oxygen

The decay pathways of structured ionization region of oxygen at different momentum transfers, i.e., 0, 0.23 a.u. (atomic unit), and 0.91 a.u., are studied by measuring the ion and the scattered electron coincidently. It is found that the dipole-forbidden superexcited states of (2σ_u)^-1(c⁴Σ_u^-)npσ_u ³Σ_g^-≤←X³Σ_g^- decay into different channels according to the principal quantum number n. The broad ridge above 35 eV, which may be due to inner-valence excited states of (2σ_g)^-1nλ or multiply excited states, is observed both at small and large momentum transfers, and its decay channel of O⁺+O is dominant.