RESEARCH NOTE: Infrared spectrum of the Ar-CO complex: observation of the upsilonCO=2 arrowleft 0 band at 4260cm-1

The spectrum of the weakly-bound van der Waals complex Ar-CO has been observed for the first time in the region of the CO vibrational overtone, using a long-path (180m) low-temperature (64K) absorption cell and a Fourier transform infrared spectrometer. The appearance of the spectrum was very similar to that studied previously in the upsilonCO=1 arrowleft 0 region. However, it was very much weaker, so a detailed analysis was only possible for the relatively uncongested K=1 arrowleft 0 and 0 arrowleft 1 subbands. The parameters determined here for these subbands should help to constrain the C-O bond length dependence of the Ar-CO intermolecular potential in future theoretical models