On O(1S) and CO(a3Π) production from electron impact dissociation of CO2

A novel method is employed to selectively detect O(1S) and CO(a 3Π) fragments following the dissociation of CO2 by electron impact. O(1S) atoms impinging on solid Xe produce a prominent emission feature at 725 nm, and less intense features at 375 and 550 nm. CO(a 3Π) molecules give a single emission feature spanning 250 to 350 nm. Time-of-flight spectra are presented for O(1S) and CO(a 3Π) from electron impact dissociation of CO2. The results for O(1S) production indicate contributions from pre-dissociation of excited states of CO2. Relative cross sections for the production of both species have been obtained. The cross section for O(1S) production has been made absolute by comparison with production of the same species from N2O. It has a threshold at 11.0 ± 0.5 eV and reaches a maximum of 1.69 x 10-17 cm2 at 50 eV. (author)