Communication: Multistate quantum dynamics of photodissociation of carbon dioxide between 120 nm and 160 nm

UV absorption cross section of CO2 is studied using high level ab initio quantum chemistry for electrons and iterative quantum dynamics for nuclear motion on interacting global full dimensional potential energy surfaces. Six electronic states-1, 2, 3(1)A' and 1, 2, 3(1)A ''-are considered. At linearity, they correspond to the ground electronic state (X) over tilde (1) Sigma(+)(g) and the optically forbidden but vibronically allowed valence states 1(1) Delta(u), 1(1) Sigma(-)(u), and 1(1)Pi(g). In the Franck-Condon region, these states interact via Renner-Teller and conical intersections and are simultaneously involved in an intricate network of non-adiabatic couplings. The absorption spectrum, calculated for many rotational states, reproduces the distinct two-band shape of the experimental spectrum measured at 190 K and the characteristic patterns of the diffuse structures in each band. Quantum dynamics unravel the relative importance of different vibronic mechanisms, while metastable resonance states, underlying the diffuse structures, provide dynamically based vibronic assignments of individual lines. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4732054]