Knowledge Bank

The torsion-rotation spectra of the isotopic methanols, $CH3OH$, $CH3OD$, $CD3OH$ and $CD3OD$ observed by D. R. Woods and C. W. $Peters1$ have been analyzed to obtain the molecular moments of inertia, the barrier heights and the Kirtman perturbation constants. The first step consisted in identifying as many sub-band origins as possible using successive trials starting with the constants given by R. M. Lees and J. G. $Baker2$. Between 30 and 40 origins were determined for each isotopic molecule with an accuracy of about $0.03cm-1$. Using these together with the very accurate microwave data of Lees and Baker, the molecular constants were found using a least squares procedure. The values of $\nu oba---\nu eale$ were generally within experimental errors. A tentative theory is proposed which connects the Kirtman perturbation constants of the various isotopic molecules. Using this theory all the experimental data, 170 in number are calculated using 21 parameters. The agreement is quite good but not as good as for the original calculation where 40 parameters in all were used. The constant $Vs$ is found to be small although not well determined, $V6=-0.15\pm 0.22$ $cm-1$.