Ab initio study of the C2O+ cation

International audienceThe first electronic states of C$_2$O$^+$ correlating to the first asymptotes of dissociation are presented. From accurate MRCI+Q / cc-pV5Z calculations, it is shown that the electronic ground state is the $X^2\Pi$ state and the first excited state the $a^4\Sigma^-$ state lying very close to the $X^2\Pi$ state, $E^{eq}(^4\Sigma^-) - E^{eq}(^2\Pi) = 2388$ cm$^{-1}$. For both states, the 3-dimensional PEFs are determined for displaced geometries in the range $-0.35 \lesssim \Delta R_{CC} \lesssim +0.6$ bohr, $-0.2 \lesssim \Delta R_{CO} \lesssim + 0.3$ bohr about the equilibrium bond lenghts and $150^{\circ} \leq \hat{CCO} \leq 180^{\circ}$. The rovibronic levels up to 2200 cm$^{-1}$ and $J=P=7/2$ are obtained for $X^2\Pi$ and the rovibrational levels of $^4\Sigma^-$ up to 5000 cm$^{-1}$ and $K=4$. The spin-orbit coupling between both states is investigated