The quenching of vibrational excited CO(nu = 2) molecules by He atoms at ultra-low temperature is examined to determine the relative efficiency of the processes that involve the exchange of a double or a single quantum of vibrational energy. We find that at low temperature the double quantum exchange cross-section is orders of magnitude smaller than for the single quantum process. This result is valid for different initial rotational states of the CO molecule. (C) 2002 Elsevier Science B.V. All rights reserved.