Experimental Study of Low Energy e-O₂ Collision Processes

Abstract Elastic scattering, vibrational excitation to v=1, 2, 3, 4 of the electronic ground state, and electronic excitation to the states a 1 Δ g and b 1 Σ g + of O 2 have been measured in a crossed beam apparatus for collision energies from nearly 0 eV to 4 eV. Differential and integral cross sections have been determined and calibrated on an absolute scale. From 15 vibrational levels of O 2 - , which could be observed as resonances in the cross sections, the spectroscopic constants for the vibrational structure of O 2 - have been derived: ω e = 135 meV and ω e χ e = 1 meV. The cross sections for vibrational excitation have the order of 10 -18 cm 2 . eV for the larger resonance peaks. Detailed cross sections have been listed in Table 1. The half width of the resonance can be estimated to Γ ≈ 0.5 meV, which corresponds to a lifetime tof 10 -12 sec for the O 2 - states. The angular dependence of pure resonance scattering is rather flat and not in accordance with the simplest theoretical model. An analysis of the angular dependence and of the rotational structure of the resonance in a somewhat extended model have been performed. - No electronically excited O 2 - states could be detected in the energy range up to 3 eV.