The 7.4μ Fundamental Vibration of Methyl Chloride

A new and fairly successful attempt has been made to resolve the fundamental vibrationrotation band ${\nu }_3$ of methyl chloride with the aid of a prism-grating spectrometer. The rotational line spacing averaged over the $P$ and $R$ branches was found to be 1.15 ${\mathrm{cm}}^{-1\mathrm{}}$. From this value the moment of inertia $A$ was calculated as 48.0×${10}^{-40\mathrm{}}$ g ${\mathrm{cm}}^2$. The $Q$ branch of this band has a satellite at a separation of about 1.0 ${\mathrm{cm}}^{-1\mathrm{}}$ toward lower frequencies. This line is taken to be the $Q$ branch for ${\nu }_3$ in C${\mathrm{H}}_3$ ${\mathrm{Cl}}^{37}$ since it agrees very well with the calculated position of this band when valence forces are assumed.