Oscillations of the methane molecule

Abstract

From a consideration of the infra-red absorption data, Dennison assigned 1304, 1520, 3019, and 4217 as the fundamental frequencies of the methane molecule, the highest, 4217, representing a symmetric expansion of the tetrahedron. In the Raman spectrum of methane, however, 4217 fails to appear, and we have instead a frequency 2918 recorded as an intense and sharp line, which is inactive in infra-red absorption and is therefore to be identified with a symmetric oscillation of the tetrahedron. I have accordingly suggested in a recent paper that the fundamental frequencies of methane are 1304, 1520, 2918, and 3019, the frequency 4217 being merely a combination of the first and the third fundamentals.