Infrared spectrum of the CO–N2 van der Waals complex: Assignments for CO-paraN2 and observation of a bending state for CO-orthoN2

Abstract

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 previously 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). In the case of the more abundant form, CO-orthoN2, an excited bending state was observed for the first time. The infrared analysis relied on precise ground state energy level differences obtained from microwave data.