Experimental measurement of the first‐ and second‐overtone spontaneous‐emissions spectrum in a low‐pressure CO/He plasma has enabled determination of the vibrational distribution up tov=30. The variation in the CO distribution as a function of CO and He partial pressure and plasma current has been correlated by a detailed model of the steady‐state energy‐transfer dynamics. The agreement between calculated and measured distributions has generated a consistent set of rate coefficients for CO/He mixtures for a temperature around 150 K.