The photodissociation dynamics of carbon dioxide cation, CO2(+), mediated by its different Ã(2)Πu,1/2(υ1,υ2,0) vibronic states has been investigated by means of time-sliced velocity map imaging. Through analysis of the recorded translational energy release spectra of photofragment CO(+), we found that the photodissociation of CO2(+) exhibits drastic change in a rather narrow energy region. A conformational barrier in the CO2(+)(Ã(2)A1) state is suggested to be ∼5600 cm(-1) relative to the CO2(+)(Ã(2)Πu,1/2(0,0,0)) state, in reasonable agreement with previous prediction.