In an experiment involving detection of a photoelectron and up to three photoions from $\mathrm{C}{\mathrm{O}}_2$ in coincidence, we observe the triple ion coincidence ${\mathrm{C}}^{+}:{\mathrm{O}}^{+}:{\mathrm{O}}^{+}$. Moreover, we observe double coincidences between doubly charged cations and singly charged cation pairs ${\mathrm{C}}^{2+}:{\mathrm{O}}^{+}$, ${\mathrm{O}}^{2+}:{\mathrm{C}}^{+}$, ${\mathrm{O}}^{2+}:{\mathrm{O}}^{+}$. These ion triplets and pairs arise from fragmentation of the triply charged molecular ion $\mathrm{C}\mathrm{O}_2{}^{3+}$. Other ion pairs—viz., ${\mathrm{C}}^{+}:{\mathrm{O}}^{+}$, ${\mathrm{O}}^{+}:{\mathrm{O}}^{+}$, ${\mathrm{O}}^{+}:\mathrm{C}{\mathrm{O}}^{+}$—arising from the doubly charged molecular ion $\mathrm{C}\mathrm{O}_2{}^{2+}$, are also observed. From an analysis of the coincidence pattern we postulate four decay modes of the $\mathrm{C}\mathrm{O}_2{}^{3+}$ ion. Kinetic energy release in the channel leading to ${\mathrm{C}}^{+}:{\mathrm{O}}^{+}:{\mathrm{O}}^{+}$ is measured, and its distribution is postulated to have four contributing precursor states.

• Received 17 March 2006

DOI:https://doi.org/10.1103/PhysRevA.74.022708