Formation of long-lived ${\mathrm{CO}}^{2+}$ via photoionization of ${\mathrm{CO}}^{+}$

The formation of long-lived ${\mathrm{CO}}^{2+}$ from ${\mathrm{CO}}^{+}$ via photoionization in the energy range 25 to 45 eV was studied experimentally at high spectral resolution. All five allowed components of a Rydberg series with an electronically excited ${}^3{\Sigma }^{+}(\nu =0)$ core are identified. Four components of a second Rydberg series with a vibrationally excited ${}^3{\Sigma }^{+}(\nu =1)$ core and structure due to the initial vibrational state of the ion beam are also discernible. The total photoionization cross section was measured with a vibrationally relaxed ${\mathrm{CO}}^{+}$ ion beam. Franck-Condon factors from ground state ${\mathrm{CO}}^{+}$ to the relevant ${\mathrm{CO}}^{2+}$ states were calculated.