Negative ion formation following inner-shell photoexcitation in CO2 studied by velocity imaging spectroscopy

The imaging technique has been applied to the negative fragment ion observation in the vicinity of the C1s and O1s ionization thresholds of CO2. The O− yield curves obtained exhibit, as well as the π* and Rydberg states bellow the ionization thresholds, doubly excited states above the thresholds. Anisotropic O− emissions with respect to the electric vector are seen on the images observed at the core-excited states, reflecting the symmetries of the states.