HIGH-RESOLUTION INFRARED-SPECTRUM AND ENERGY-LEVELS OF THE WEAKLY-BOUND COMPLEX, CO-PARAH(2)

The infrared spectrum of the weakly bound complex CO-paraH(2), which a ccompanies the fundamental band of CO in the 4.7 mu m region, has been recorded at high resolution (0.005 cm(-1)) using a long-path (200 m), low-temperature (48 K), absorption cell. A total of 135 transitions, constituting almost all of the observed lines, has been rotationally a ssigned in terms of 44 discrete quantum states of the complex, and the positions of these energy levels have been determined to high accurac y (< 0.001 cm(-1)) for both the nu(CO) = 0 and 1 vibrational states. T he binding energy of the complex, relative to the zero-point level, wa s determined to be about 22 cm(-1). Predicted microwave and millimeter wave frequencies are given for the pure rotational spectrum of CO-par aH(2). The energy level pattern derived here provides the information needed to make precise determinations of the CO-H-2 intermolecular pot ential energy surface in the attractive region. However, determination of the dependence of this surface on the orientation of H-2 within th e complex will have to await the analysis of the more complicated spec trum of CO-orthoH(2). (C) 1998 American Institute of Physics.