Millimeter-wave study of the CO-N2 van der Waals complex:: new measurements of CO-orthoN2 and assignments of new states of CO-paraN2

Rotational transitions of the CO-N-2 van der Waals complex have been measured using the intracavity OROTRON jet spectrometer in the frequency range of 83-133 GHz. For the CO-orthoN(2) spin modification, the observed and assigned 21 rotational transitions belong to the Q- and P-branches of the K= 1-0 subband. They complete the previous observation of the corresponding R-branch transitions. In the case of the less abundant form, CO-paraN(2), a new K= 1 state, representing simultaneous rotation of both monomers, was detected for the first time. A total of 31 rotational transitions of CO-paraN(2) were assigned to two subbands connecting this new K= I state with already known lower K= 0 and I states. The assignments relied in part on energy level differences obtained from precise microwave data. The origin of the newly observed state was determined to be 3.41 cm(-1) relative to the K= 0 ground state of CO-paraN(2). The analysis yielded rotational parameters, centrifugal distortion parameters and nuclear quadrupole coupling constants due to the presence of two equivalent N-14 nuclei for both CO-orthoN(2) and CO-paraN(2). (c) 2006 Elsevier B.V. All rights reserved.