3500-A1A2 - X-1A1 TRANSITION OF FORMALDEHYDE-H2 D2 AND HD1 VIBRATIONAL AND ROTATIONAL ANALYSES

The polarizations of representative bands in the 1A2-1A1 systems of H2CO, D2CO, and HDCO are determined by analysis of rotational fine structure of the absorption spectra. In addition to bands of types A, B, and C, there are observed Coriolis couplings about inertial axes a, b, and c. From these identifications the six excited-state fundamental vibrational frequencies are found and confirmed for each molecule: All except the CH stretching frequencies are reduced by at least 25% on electronic excitation. Overtones of the out-of-plane bending mode are discussed in detail. The upper state geometrical parameters obtained from the rotational fine structure are r0(CH) = 1.092 A ̊, r0(CO) = 1.321 A ̊, ∠HCH = 121.5° and an out-of-plane angle of 20.5°. © 1969.