Dissociative ionisation of O2and CO2by electron impact: Energy and angular distributions of fragments

The mass spectrometric apparatus and the method of studying the processes of dissociative ionisation of atmospheric molecules under collisions with electrons in crossed electron and gas dynamical molecular beams are described. The energy spectra and the angular distributions of O + (O 2 , CO 2 ) and CO + (CO 2 ) ionised fragments were measured over the incident electron energy range 45-150 eV. On the basis of the known potential curves and the appearance potentials using the measured energy and angular distributions the possible mechanisms of ionised fragment production are discussed. It is shown that, besides the main process of CO 2 + predissociation, the fraction of ionised fragments is produced in the process of direct dissociation.