The infrared spectrum of the Ar-CO complex Comprehensive analysis including van der Waals stretching and bending states

The infrared spectrum of the weakly-bound Ar-CO van der Waals complex in the 2150 cm-1 region of the CO stretch has been studied using a continuous supersonic slit jet expansion coupled with a tunable laser spectrometer, and also with a cooled (57 K) long-path cell coupled with a Fourier transform spectrometer. Seven new subbands were observed, and previously observed bands were observed in greater detail. Four substates were thus identified for the first time, including the excited van der Waals stretching state, v 3 = 1, and the excited bend, v 2 = 1, within the ground CO stretching state, v CO = 0. A comprehensive simultaneous analysis was made of all the existing infrared and microwave data on the complex for levels with K < 5, in order to obtain an accurate and self-consistent set of substate origins, rotational parameters, and centrifugal distortion parameters. A strong Coriolis interaction between K = 1 of the excited bend and K = 0 of the excited stretch was analysed in detail.