Infrared spectrum of the CO-N-2 van der Waals complex: Assignments for CO-paraN(2) and observation of a bending state for CO-orthoN(2)

The infrared spectrum of the weakly bound complex CO-N-2 has been studied u sing a pulsed supersonic slit-jet and a rapid-scan tunable diode laser. A m irror system giving 182 passes of the laser through the jet helped to give improved spectra with lower effective rotational temperatures (approximate to 0.5 to 4 K) and less interference by CO dimer transitions. In the case o f the CO-paraN(2) spin modification, for which only one subband was previou sly known, over 10 linked subbands were assigned in terms of three ground ( upsilon(CO) = 0) state stacks of levels (with K = 0 and 1), and 7 excited s tate (upsilon(CO) = 1) stacks (with K = 0, 1, and 2). In the case of the mo re abundant form, CO-orthoN(2), an excited bending state was observed for t he first time. The infrared analysis relied on precise ground state energy level differences obtained from microwave data. (C) 2000 American Institute of Physics. [S0021-9606(00)00326-3].