Knowledge Bank

Some of the $anomalies1$ reported in the pure rotation spectrum of fluoroform in the excited vibrational state $v6=1$ can be explained with the assumption that the two unperturbed levels $K=0,l6=\pm 1$ and $K=\pm 2,l6=\pm 1$ lie very close to each other. The coupling between these two levels due to l-type resonance is then much stronger than usual. This is a good example of the situation previously described as ``accidentally strong essential $resonance″2$. $\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}$Supported in part by the Air Force Cambridge Research Laboratories O.A.R. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ C. C. Costain, J. Mol. Spectroscopy, 9, 317 (1962). $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ G. Amat and H. H. Nielsen, J. Chem. Phys. 36, 1859 (1962).