Infrared spectrum of the CO-OCS van der Waals complex in the carbon monoxide stretching band

The rotation-vibration band of the weakly bound OCS-CO complex which corres ponds to the carbon monoxide CO vibrational mode has been detected using a pulsed supersonic slit-jet expansion and a tunable infrared diode laser pro be. The band was found to have a parallel (Delta K-a = 0) structure, in goo d agreement with previous determinations of the structure of the complex. I ts rotational structure appeared to be affected by numerous small (similar to 0.01 cm(-1)) perturbations in the upper state which probably are due to interactions with bound levels of a lower lying vibrational state of the co mplex. The band origin is located with a relatively small shift of + 1.23 c m(-1) from that of the free CO molecule.