Knowledge Bank

Since our last $report\ast$ on the high resolution rotational spectrum of isocyanogen, CNCN, we completed measurements of the high resolution FT-IR spectrum of this species between 150 $cm-1$ and 2400 $cm-1$ using the Bruker IFS 120 HR. The $C\equiv N$ stretching band systems $\nu 1$ and $\nu_{2} $ centered around $2302.0cm-1$ and $2059.7cm-1$, respectively, were observed with an unapodized resolution of $0.003cm-1$ which is just below the Doppler linewidth. We obtained signal to noise ratios of up to 300 and 450 for the lines of the fundamental bands $\nu 1$ and $\nu 2$, respectively. This made possible the assignment of hot band transitions in both band systems originating from the states with up to 3 quanta of the cis-bending mode $\nu 5$, the singly excited trans bending mode $\nu 4$, and the combination state $(\nu 4\nu 5)=(11)$. Up to now we have assigned around 2500 lines in the two band systems. In the case of the $\nu 2$ fundamental band we expect to identify the transitions of the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C$ isotopomers in natural abundance. We also have assigned around 1000 transitions in the bands due to the trans and cis bending modes $\nu 4$ and $\nu 5$ located at $463.5cm-1$ and $194.8cm-1$, respectively. This will allow the determination of the vibrational energy level diagram for the bending states starting from the ground state and the corresponding bending stacks associated with $\nu 1$ and $\nu 2$. Adjusted spectroscopic constants of an effective hamiltonian will be presented.