Knowledge Bank

The infrared spectra of $CH3C1$, $CH3Br$, $CD3BrC12H31,C13H3I$, and $C12D3I$ have been re-examined between 3000 and $500cm-1$ using high resolving power. Considerable improvement has been obtained over nearly all previous observations on these molecules. In $CH3I$ it has been possible to resolve clearly a regular fine structure between the Q branches of the perpendicular frequency at $880cm-1$. This has been possible because the P and R lines arising from various Q branches happen to coincide or nearly coincide. Improved values have been obtained for a large number of the molecular constants. These new values show some interesting features which will be discussed.