Fragmentation of CO2 into C++O++O,in collisions with protons

The fragmentation of CO2 has been investigated in 25 keV H+ + CO2 collisions using an electron-ion-ion triple coincidence technique. In this letter we focus on the three-body fragmentation into the C+ + O+ + O final state. A comparison between the measured correlation of C+, O+ and O momenta and simple kinematic models allows us to demonstrate that in the present case, a rather unexpected two-step process with formation of a CO2+ ion as an intermediate state occurs. This result is at variance with the conclusions of other authors achieved in collisions of photons and electrons with the dioxide molecule. Kinetic energy release distributions in the two steps of the dissociation process are also deduced from experiment; the distributions found for the fragmentation of CO2+ into C+ + O+ are found to be very similar to those measured by other authors in collisions of various particles (photons, multi-charged ions) with CO molecules at high enough collision energy.