A new ion translational energy spectrometer has been developed to carry out low-energy, gas-phase ion-molecule collision experiments which aim to probe molecular potential energy surfaces. The collisional technique employed relates small changes in the kinetic energy of a projectile ion after it has undergone collision with a static neutral atom/molecule to changes in the overall potential energy of the collision system; information can be furnished about the interaction potential between the projectile and the target. First measurements are reported of a high resolution target excitation spectrum obtained in 1.8 keV collisions of H₂⁺ ions with N₂. New results pertaining to collision-induced dissociation of CO₂⁺ ions are presented and discussed in terms of potential functions of low-lying electronic states of the molecular ion.