FTIR Spectra of the 2nu₄, nu₄+nu₆ and 2nu₆ Bands of Formaldehyde

F. Ito, T. Nakanaga, and H. Takeo
[Spectrochimica Acta, Vol.50A, pp.1397-1412, 1994]

High resolution IR spectra of the overtones and the combination band of the nu₄ and nu₆ modes of formaldehyde (2nu₄, nu₄+nu₆ and 2nu₆) were measured in the region of 2200-2650 cm^-1 using FTIR. The combination band nu₄+nu₆, whose dipole transition is forbidden from molecular symmetry, was observed due to the intensity borrowed from the other bands. The observed frequencies were analysed by a Hamiltonian in which A-type Coriolis interactions and Darling-Dennison interaction were taken into account. The ratio and the relative sign of the transition dipole moments of the overtone bands, mu₂nu₄ and mu₂nu₆, have been determined by analysing the intensity distribution of the vibration-rotation lines.