Knowledge Bank

We reported a preliminary analysis of the $\nu 3$ fundamental band of $SH3+$ at this meeting a year $ago1$. The vibration-rotation levels in the $\nu 31$ state were found perturbed. The molecular constants in the $\nu 3=1$ state were obtained by excluding the severely perturbed lines, whereas the ground state constants were well determined by using the combination differences. Ab initio calculations have predicted that the $\nu 1$ fundamental band lies very close to the $\nu 3$ fundamental band within several $cm-1$. The assignments of the $\nu 1$ fundamental, however, had not been easily done presumably due to much smaller intensity, until a systematic sorting of the ground state combination differences was performed on all the unassigned lines. A simultaneous analysis of the $\nu 1$ and $\nu 3$ bands was made by including the higher-order vibration-rotation interaction terms $(\Delta (K\ast \ast \ell )=\pm 3)$, and the molecular constants were determined for the $\nu 1-1$ and $\nu 3=1$ states.