High-Resolution Spectroscopy of the X-A Transition of the Carbon Monoxide Dication CO${}^{2+}$

Abstract

We report rovibronic spectra of the A ${}^3{\Sigma }^{+}$($v^{\prime }=0-2$) - X ${}^3{\Pi }_{\Omega }(v=0)$ rovibronic transitions ($|\Omega |=0,1$ and 2) of the CO${}^{2+}$ doubly-charged molecular ion. Spectra were recorded at high resolution ($\sim 5$~cm${}^{-1}$) in a fast beam of CO${}^{2+}$ molecules by detecting the Coulomb explosion of the molecules upon excitation to the A state. Measurements were guided by \textit{ab initio} calculations which then assisted the assignment of the observed spectral features. Our results resolve the spin-orbit splittings of the ground vibronic state X ${}^3{\Pi }_{\Omega }(v=0)$, but not the rotational structure of the bands due to spectral congestion, and provide spectroscopic information on CO${}^{2+}$ with unprecedented resolution. In doing so they expand our knowledge of this benchmark doubly charged molecular ion and expand the short list of doubly charged molecules studied at high resolution.