Knowledge Bank

We report the first observation of the $\nu 1$ (N-H stretch) band of protonated cyanoacetylene ($HCCCNH+$) which is supposed to play an important role in interstellar chemistry by using a difference frequency laser system at $NRC.HCCCNH+$ was generated in a modulated hollow cathode discharge through a gas mixture of $HCCCN(\sim 20mTorr)$ and $H2(\sim 400mTorr)$. It has been found, however, that the observation should be done at high flow rate of gas mixture to prevent the parent molecule from decomposition. The band origin and the rotational constants have been obtained by a least squares analysis.