Single-, double-, and triple-photoionization cross sections of carbon monoxide (CO) and ionic fragmentation of CO+, CO2+, and CO3+

Abstract

Single-, double-, and triple-photoionization processes of carbon monoxide (CO) have been studied in the photon-energy region of 37--100 eV by use of time-of-flight mass spectrometry and a photoion-photoion-coincidence method together with synchrotron radiation. The single-, double-, and triple-photoionization cross sections of CO are determined. Ion branching ratios and the partial cross sections for the individual ions respectively produced from the precursors ${\mathrm{CO}}^{+}$ and ${\mathrm{CO}}^{2+}$ are determined separately at excitation energies where the molecular and dissociative single- and double-photoionization processes compete. The threshold for the molecular double photoionization was found to be 41.3\ifmmode\pm\else\textpm\fi{}0.2 eV. Furthermore, in single photoionization, the production of ${\mathrm{CO}}^{+}$ is dominant whereas with double photoionization dissociation becomes dominant.