Global rovibrational analysis of HCCNC based on infrared and millimeter-wave spectra

New microwave and millimeter-wave spectra up to 200 GHz of isocyanoacetylene (HCCNC) have been recorded. About 675 lines have been assigned to 111 vibrational states with energies up to 1700 cm(-1). In previously recorded infrared spectra in the 600-2000 cm(-1) domain, 53 new infrared bands have been assigned and analyzed. These concern upper vibrational states up to energies close to 1900 cm(-1), which are combinations of the three bending modes (nu(5) to nu(7)) and the lowest energy stretching mode nu(4). The assignments were made possible thanks to a global rovibrational analysis progressively applied to all available data. Good agreement has been obtained, and a set of 155 molecular parameters has been determined. Our analysis suggests that the term directly coupling 2 nu(6) and nu(5) + nu(7) states (k(5667)) is to be added to our model, and also Coriolis interactions between nu(6) and 2 nu(7) states on one hand, and between nu(5) and nu(6) + nu(7) states on the other hand. (C) 2000 Academic Press.