The Infrared Absorption Bands of Methane

The two fundamental vibration-rotation bands ${\nu }_3$ and ${\nu }_4$ of methane have been remeasured with greater resolution than that available in the earlier investigation of Cooley. Whereas the band at 3.3μ showed no essentially new details, the fundamental band at 7.7μ was found to possess a somewhat more complex rotational structure than was observed by Cooley. Many of the lines given in Cooley's curve are here resolved into groups of closely spaced components. The separation between the components within a group appears to increase with the ordinal number of the line counted outward from the center of the band. In addition to these measurements, the two combination bands ${\nu }_1+{\nu }_4$ at 4218 ${\mathrm{cm}}^{-1\mathrm{}}$ and ${\nu }_3+{\nu }_4$ at 4315 ${\mathrm{cm}}^{-1\mathrm{}}$ have been at least partially resolved and appear to have line spacings of about 5.3 ${\mathrm{cm}}^{-1\mathrm{}}$ and 13.5 ${\mathrm{cm}}^{-1\mathrm{}}$, respectively.