Electron Emission from Fragmentation of CO₂ by Fast Proton Impact

Single ionization of CO2 by 6 MeV proton impact has been studied by measuring in coincidence the momentum vectors of the emitted electron and the charged nuclear fragment CO+2, CO+ or O+, respectively. The experimental data have been compared with the predictions of a state of the art CDW-EIS (continuum distorted wave-eikonal initial state) calculation for molecular orbitals. A good qualitative agreement is observed even though the vibrational motion of the molecule is not taken into account in the model. The low-energy electron spectra show a rich structure which may be attributed to the presence of molecular excitation channels which undergo radiationless decay, via autoionization and also via predissociation. This interpretation is supported by photoionization studies of CO2