Experimental Detection of HOC+by Microwave Spectroscopy

Microwave spectroscopy has been employed to make the first definite experimental observation of the ionic metastable isomer HO${\mathrm{C}}^{+}$. Its $J=0\mathrm{}\to 1$ transition and those of its ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ isotopic variants have been detected in laboratory dc glow discharges. Extensive chemical, spectroscopic, and theoretical evidence permits conclusive identification of these spectra. Comparison of the substitution bond lengths [${\mathcal{r}}_s\left(\mathrm{CO}\right)=1.1595\mathrm{}$ Å and ${\mathcal{r}}_s\left(\mathrm{OH}\right)=0.9342\mathrm{}$ Å] to ab initio structures strongly supports a large-amplitude (low-frequency) bending vibration.