The Near Infrared Absorption Spectrum of Methane

The infrared absorption spectrum of methane between 1.4{μ} and 2.6{μ} was obtained with an infrared spectrometer having a grating of 5000 lines to the inch. Strong bands were found in the 1.6{μ} and 2.3{μ} regions. The fine structure of the 2.3{μ} band was resolved in the first order spectrum. The fine structure of the 1.6{μ} band was resolved in the second order but not in the first order spectrum. Only at the 2.20{μ} and the 1.66{μ} bands could the fine structure be measured. The 2.20{μ} band has spacing of 10.7 cm^-1, giving for the value of the moment of inertia 5.17×{}10^-40 c.g.s. units. The corresponding values for the 1.66{μ} band are 10.4 cm^-1 and 5.32×{}10^-40 c.g.s. units. These results are quite close to the values of 9.77 cm^-1 and 5.66×{}10^-40 c.g.s. units found for the 3.31{μ} band by Cooley.