Electron impact threshold excitation of CO by the trapped-electron method

A threshold excitation spectrum of CO, obtained with an improved resolution, is presented and much structure is identified. Observation of the behaviour of the excitation cross section in the threshold region leads to evidence supporting the assignment of the configuration CO - . . . 1 pi 4 5 sigma 6 sigma 2 2 Sigma + to the resonance at 10.04 eV and also reveals resonances at 10.6 eV and 11.1 eV that form a series, with the 10.04 eV resonance as lowest member, which are associated with the b 3 Sigma + and B 1 Sigma + states.