The ?1 A2 - X1 A1 system of formaldehyde, H2C=0: Reanalysis of the 110410 and 510 bands

A frequency-doubled dye laser was used to excite the fluorescence of formaldehyde in the region 31 099-31 185 cm-1. Using iodine standard lines, the wave numbers of nearly 300 lines of formaldehyde have been determined. Since these lines form only part of the overlapping 110410 and 510 bands of the ?1A2- X1A1 system, complete coverage of these bands was obtained using a Fourier-transform spectrometer. Some of the frequency-doubled lines were used as standards. Rotational analysis has been carried out and improved molecular constants obtained. The two bands show a Coriolis interaction. However, while earlier workers found an interaction proportional to Ka, we obtain a cubic dependence on this quantum number.