Chemiluminescence from vibrationally excited carbon monoxide formed by the reaction CS+O→CO(v)+S was observed in CS2/O2and CS2/O2/N2O flames to which an electric discharge was applied. Although the total amount of chemiluminescence increased with increasing discharge current probably due to enhanced reaction rates as a result of radical formation, the vibrational distribution was quenched, becoming thermal in character. The thermalization is attributed to superelastic electron collisions [e+CO(v)→e+CO(v−1)]. The technique demonstrates a sensitive method for detecting collisional transfers between excited states by separating the perturbation (electron collisions) from the initial excitation mechanism (chemical reactions).