Translational-energy spectroscopy (TES) of Cl2+ and Cl+ ions together with state-selected single-electron capture (SEC) reactions of 6 keV Cl2+ ions from rare-gas targets (except He) have been carried out using a novel translational-energy spectrometer. Experimentally observed transitions in the TES of both ions indicate that, in addition to the 4S ground state, the Cl2+ incident ion beam contained the excited states 2D and 2P. No excited states were observed in the incident Cl+ ions but, following collisions with He atoms, the 1S excited state is populated. The use of TES to identify the excited states within the incident ion beam allows more reliable assignments of the observed reaction channels in the SEC spectra.