A velocity map imaging (VMI) spectrometer to investigate photo dissociation dynamics was designed and fabricated. This spectrometer combines a skimmed molecular beam with a multi-stage time-of-flight mass spectrometer equipped with position-sensitive detection. Investigations on the 266 nm photo dissociation of o-xylene leading to {sp²}C–C{sp³} bond cleavage resulting in CH₃and C₆H₄CH₃ fragments reveal that the kinetic energy partitioning in the centre-of-mass frame is almost identical in both the fragments indicating a single dissociation mechanism with CH₃ radical produced almost exclusively in the m= 0 level of the ground electronic state. The weakening of the {sp²}C–C{sp³} bond by about 17 kcal mol^-1 in the cationic ground state relative to the neutral ground state of o-xylene facilitates the dissociation, propelled by the three-photon absorption process.