XUV-pump IR/VIS-probe dissociative ionization of CO₂

Following the sudden single ionization of CO₂ in ultrashort extreme ultraviolet pump pulses, we propagated, exposed to delayed 780 or 400 nm probe-laser pulses, the coupled nuclear motion in CO₂⁺ on the A²Π_u, B²Σ_u⁺, C²Σ_g⁺, a⁴Σ_g^-, and b⁴Π_u of CO₂⁺ potential-energy surfaces of the excited molecular cation, including all vibronic degrees of freedom. We calculated potential-energy surfaces, diabatic couplings, and probe-laser-induced dipole couplings between BO states ab initio and heuristically modeled spin-orbit couplings. Based on our numerical results, we (i) scrutinize the relative importance of non-adiabatic, dipole, and spin-orbit couplings during the dissociation of CO₂⁺ into O(³P_g) + CO⁺( X²Σ⁺) and O⁺(⁴S_u) + CO(X¹Σ⁺), (ii) provide ro-vibrational-excitation distributions of the CO⁺ fragments, and (iii) discuss pump-probe delay-dependent kinetic-energy-release spectra. Addressing the nuclear dynamics near the conically intersecting A²Π_u, B²Σ_u⁺, states of CO₂⁺, we (iv) reproduce the valence-hole oscillation period of 115 fs measured by Timmers et al., Phys. Rev. Lett. 113, 11303 (2014). In addition, we (v) predict and characterize in terms of quantum beats between specific stationary vibronic states a 3.1~ps fragment-yield oscillation.