INFRARED-ABSORPTION SPECTROSCOPY OF THE CO-AR COMPLEX

The rotation-vibration spectrum of the weakly bound complex COAr has been studied in the 2140 cm-1 region of the fundamental band of CO. Data were obtained from two different experiments: first, a pulsed slit-jet supersonic expansion and a tunable diode laser source; and second a long-path low-temperature static gas cell and a Fourier transform spectrometer. The low rotational temperature and narrow line width of the jet expansion data were complementary to the higher J-values and broad coverage of the static cell data. The observed spectrum was approximately that of a T-shaped near-prolate asymmetric rotor molecule. About 370 transitions were assigned to 6 perpendicular subbands with K = 3-2, 2-1, 1-0, 0-1, 1-2, and 2-3. No parallel (ΔK = 0) subbands were observed. The observed B rotational constant of the complex in its ground state, 0.0691 cm-1, corresponds to an effective intermolecular separation of about 3.850 Å. The observed A rotational constant of about 2.47 cm-1 is not too far from the B value of the CO monomer, 1.92 cm-1, as expected for the approximately T-shaped effective geometry of the complex. © 1992.