Tunable infrared diode laser absorption (TDLAS) and Fourier transform infrared absorption spectroscopies (FTIR) have been utilized to characterize the translational, rotational and vibrational distributions of CO in an acetone/argon DC plasma at total pressures ranging from 4 to 5 Torr and currents of 0.1-0.3 A. A broad vibrational distribution of CO was observed with gradually decreasing intensities from the fundamental band to v = 12 <-- 11. When nitrogen was added to the plasma, the distribution is narrower, due to the efficient energy transfer between CO and N-2 molecules. The measured translational temperature in such plasmas ranged from 400-550 K. The rotational distribution can generally be fitted to a Boltzmann distribution within each vibrational level although the rotational temperature is highest for the lowest vibrational quantum number. (C) 2004 Elsevier B.V. All rights reserved.