Infrared spectrum of the Ar-CO complex: observation of the (v)co=2 <- 0 band at 4260 cm (-1)

The spectrum of the weakly-bound van der Waals complex Ar-CO has been obser ved for the first time in the region of the CO vibrational overtone, using a long-path (180 m) low-temperature (64 K) absorption cell and a Fourier tr ansform infrared spectrometer. The appearance of the spectrum was very simi lar to that studied previously in the nu(CO) = 1 <-- 0 region. However, it was very much weaker, so a detailed analysis was only possible for the rela tively uncongested K = 1 <-- 0 and 0 <-- 1 subbands. The parameters determi ned here for these subbands should help to constrain the C-O bond length de pendence of the Ar-CO intermolecular potential in future theoretical models .