Knowledge Bank

The band system of the low-lying CCN bending mode $\nu 7$ of the pseudohalofulminate NCCNO around $85cm-1$ has been recorded by high resolution FTIR spectroscopy to supplement our previous investigation of the pure rotational spectrum, which had revealed some slight, but significant indications of $quasilinearitya$. Besides rovibrational transitions of the fundamental band, rovibrational transitions belonging to the first, second, third, and fourth hot band could be assigned. Using a conventional linear-molecule type $Hamiltonianb$, these rovibrational transitions have been analyzed together with the pure rotational transitions. The results of this analysis confirm a moderate anharmonicity in the CCN bending potential. To quantify this anharmonicity, the combined data have been subjected to a semirigid bender analysis, which resulted in a rather flat bending potential with a significant quartic contribution.