Intensités absolues des transitions de vibration–rotation des bandes ν2 et ν4 du méthane 12CH4

Abstract

The general expansion of the transformed dipole moment of tetrahedral XY4 molecules, considered by Loete, is used to study the line strengths of the ν2 and ν4 bands of methane, 12CH4. This systematic expansion, written in tensorial form in the Td group, considers all the interactions to a given order and, contrary to the polynomial methods, it allows an accurate interpretation of the strength perturbations. The two bands ν2 and ν4 have been chosen to show the possibilities of the model. They have been studied separately, and then in interaction. In each case, the experimental precision has been obtained for both strong and weak lines. The isolated band scheme requires two and five parameters for the ν2 and ν4 bands respectively, while three parameters are sufficient in the dyad scheme.