Knowledge Bank

When a Ne:HCN sample is codeposited at approximately 5 K with a beam of neon atoms that have been excited in a microwave discharge, infrared absorptions of HNC, $HCN+$,and $CN-$ appear. The absorptions of HNC isolated in solid neon are considerably closer to the gas-phase band centers than are the previously reported argon-matrix absorptions. The CH-stretching fundamental of $HCN+$ is identified, and the two stretching force constants of $HCN+$ are determined, using the isotopic data obtained in this study and the CN-stretching frequencies of $HCN+$ and $DCN+$ obtained in earlier photoelectron spectroscopic studies. In the inert, nonpolar environment provided by the neon matrix, the infrared absorption of $CN-$ appears at $2053.1cm-1$, very close to the position obtained in two recent ab initio calculations. $HCN+$ photoisomerizes to $HNC+$ with a threshold in the near infrared spectral region, consistent with an earlier ab initio calculation of the position of the transition state for this process. The reverse photoisomerization has also been observed at somewhat higher energies. All three vibrational fundamentals of $HNC+$ have been identified, and the stretching force constant have been determined. In all but the most dilute samples, $HCNH+$ is also stabilized in detectable amounts. Electron photodetachment from $CN-$ results in charge neutralization of $HCN+$ and $HCNH+$ and in growth of the infrared absorption of CN.