Knowledge Bank

The infrared spectrum of the weakly-bound complex $CO-N2$ has been studied using a pulsed supersonic slit-jet and a rapid-scan tunable diode laser. A mirror system giving 182 passes of the laser through the jet helped to give improved spectra with lower effective rotational temperatures (0.5 to 4 K) and less interference by CO dimer transitions. In the case of the $CO-paraN2$ spin modification, for which only one subband was $previouslya$ known, over 10 linked subbands were assigned in terms of three ground $(vCO=0)$ state stacks of levels (with K= 0 and 1), and 7 excited state $(vCO=1)$ stacks (with K = 0, 1, and 2). The infrared analysis relied sin precise ground state energy level differences obtained from microwave $data.b$ There is a strong Coriolis interaction between the K = 0 and 1e stacks of levels in both the ground and excited states. However, their energy ordering changes, with K = 0 being lower for $vCO=0$, and K= 1 being lower for $vco=1$, For the more abundant nuclear spin modification of the complex, $CO-orthoN2$ an excited bending state was observed for the first time. The bending frequency is $4.67cm-1$.