Ionic fragmentation of K-shell excited and ionized CO.

Abstract

Quantitative ion yields from photoionization of gaseous CO have been measured with time-of-flight mass spectrometry and photoion-photoion coincidence techniques using synchrotron radiation from 270 to 360 eV and from 515 to 615 eV, in the region of C 1s and O 1s excitation and ionization. Dissociative multiple-ionization efficiencies, ion-branching ratios, and the relative yields of all possible ionization reactions are derived. The distributions of kinetic energies released to the (${\mathrm{C}}^{+}$+${\mathrm{O}}^{+}$) and (${\mathrm{C}}^{2+}$+${\mathrm{O}}^{+}$) pairs are measured. Very large contributions of symmetric dissociative double ionization producing ${\mathrm{C}}^{+}$ and ${\mathrm{O}}^{+}$ are found, even in the region of the 1s\ensuremath{\rightarrow}${\ensuremath{\pi}}^{\mathrm{*}}$ resonances. The results are discussed in the context of the autoionization and Auger electron spectroscopy of core-excited CO and with the aid of recent calculations of the potential curves of ${\mathrm{CO}}^{2+}$. The relationship between the present results and those for photon-stimulated desorption following core excitation and ionization of solid and chemisorbed CO is explored.