Differential cross sections for dissociative attachment in CO

An electron-impact spectrometer is described which, by means of a modification, is able to observe energy and angular distributions of ion fragments produced by molecular dissociation processes with a good precision and sensitivity. ${\mathrm{O}}^{-}$ ion formation through dissociative electron capture in CO has been studied. An analysis of the observed ${\mathrm{O}}^{-}$ differential cross sections using the theory of O'Malley and Taylor and two partial waves indicates that the two reactions leading to ${\mathrm{O}}^{-}$ both proceed through a ${}_{}{}^2{}_{}{}^{}\Pi$ resonant state. Both resonances appear to have a ${\sigma }^2{\pi }^3{\pi }^2$ configuration by analogy with isoelectronic NO, and their parents would be the $a^{\prime }{}_{}{}^3{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$, for the process with a 9.62-eV threshold, and possibly the $d{}_{}{}^3{}_{}{}^{}\Delta$ state, for the process with an onset at 10.88 eV.