Knowledge Bank

Following last year's talk, we have continued detailed examination of the weak in-plane methyl-rocking band of the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3OH$ isotopomer of methanol. The assignments for the ground torsional state have now been completed up to $K=13$ for all the torsional symmetries. The Q-branches of these n=O transitions form the novel twin peak Q-branch feature seen for this band in a number of isotopomers of methanol. We showed earlier that the twin peaks arise simply from the accidental piling up of these sub-branch heads in two distinct regions due to a significant difference in torsional structure between the rocking state and the ground state. This difference was further supported earlier by the observation of a few first excited torsional sub-branches of the torsional index $\tau =2$ only. They appear about $50cm-1$ above the main n=O Q-branch feature, and suggested that the torsional barrier height in the rocking state was about 30% higher than that in the ground state. Further first excited torsional sub-branches have been found recently. However, the origins of these series are located in the same region as the main ground torsional features. This will allow us to construct the first excited torsional energy pattern as fully as possible. This work is still in progress. The available results, together with some new FIR laser assignments for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3OH$, will be discussed.