FTIR SPECTRA OF THE 2-NU(4), NU(4)-NU(6) BANDS OF FORMALDEHYDE(NU(6) AND 2)

High resolution IR spectra of the overtones and the combination band o f the nu4 and nu6 modes of formaldehyde (2nu4, nu4 + nu6 and 2nu6) wer e measured in the region of 2200-2650 cm-1 using FTIR. The combination band nu4 + nu6, whose dipole transition is forbidden from molecular s ymmetry, was observed due to the intensity borrowed from the other ban ds. The observed frequencies were analysed by a Hamiltonian in which A -type Coriolis interactions and Darling-Dennison interaction were take n into account. The ratio and the relative signs of the transition dip ole moments of the overtone bands, mu2nu4 and mu2nu6, have been determ ined by analysing the intensity distribution of the vibration-rotation lines.