Knowledge Bank

The $\nu 1$ and $\nu 2$ fundamental bands of $HCNH+$ and the $\nu 1$ fundamental band of $DCNH+$ were recently observed in the laboratory by difference frequency laser spectroscopy. In the present work, measurements of the hot bands $(\nu 1+\nu 4\leftarrow ,\nu 1+\nu 5\leftarrow \nu 5)$ have been made possible with a hollow-cathode discharge cell. Also the measurement has been extended to the isotopic species, $HCND+$ and $H13CNH+$. By combining these data with the already existing data on the normal species and $DCNH+$, the $rs$ structure of this ion has been obtained with the aid of the first moment condition. The bond lengths are in very good agreement with the calculated values $(re)$ by Botschwina.