Knowledge Bank

We have recorded the far-infrared spectrum of $CH3CO3$ and $C2O6$ in the regions of the forbidden torsional fundamentals under relatively large pressure-pathlength conditions. The observations were made using a modified Bomem spectrometer, with an absorption path of 20 m, a temperature of 230 K, pressures of 50-80 torr, and a resolution of $0.01cm-1$. The most prominent features of the spectra are the unresolved Q-branches of the various torsional components of the $\nu 4-1-0$ band of $C2O6$ with an origin at about $208.5cm-1$, and of the $\nu 6=1-0$ band of $CH3-CO3$ with an origin at about $252.70cm-1$. To lower frequencies there are the partially-resolved Q-branches of the $\nu -2-1$ hot bands at about $193.0cm-1$ for $C2O6$ and $227.9cm-1$ for $CH3CO3$. The P- and R-branches of the fundamental consist of peaks about $0.2cm-1$ wide due to unresolved clusters. These peaks can be followed up to $J=30$ in both branches. We have also recorded both low (230 K) and room temperature spectra of the lowest lying allowed fundamental bands around $594cm-1(C2O6)$ and $679cm-1(CH3CO3)$ with a resolution of $0.0013cm-1$. Over 1000 transitions have been identified in the , and -branches for each molecule. In addition, the millimeter wave spectrum of $CH3CO3$ has been recorded at around 240-360 GHz in the $v6-0$ and 1 torsional states for several R-branch transitions. K-splitting has been observed for both states, but not $\sigma$-splitting. We will present results for the ground vibrational state of both isotopes based on the analysis of the torsional fundamental together with combination differences obtained from the lowest lying allowed fundamentals and their corresponding hot bands.